I used to think that Bohm's theory made a lot more sense than orthodox QM, and I thought that the only reason that people held to the orthodox view was inertia or a kind of philosophical malaise left over from Bohr's ideas.
I agree, Bohm theory isn't the real thing. As Einstein said, it was too cheap. Its main virtue was that it had served as a direct counterexample to the von Neumann no-go theorem for any hidden variables.
The origin of its inadequacy and the main source of its difficulties was in retaining the QM's 3N dimensional phase space for the N particles. That made it easier to map into the QM, to show the equivalence of their predictions, but at the cost of turning the theory into conceptual dead-end.
There are several much better alternatives, in particular the nonlinear field theories of A.O. Barut and E.T. Jaynes. They went back to the Schrodingers original idea when he came up with his equation: he intended to take the classical Maxwell equations coupling charged particles and the EM fields, then replace the Newtonian point particle currents with his Psi field (the wave function) currents. Unfortunately, the resulting system is a set of nonlinear partial differential equation, which were far beyond the mathematical techniques of his day. Additionally, an unfortunate computational error he made in one of his initial tries with this approach (on a simpler example), convinced him incorrectly that it wouldn't work even if he could carry the fuller calculations out. So he gave up on it.
It was only in early 1970s that Jaynes noticed the error and carried out more complicated calculations, finding that it actually works. He then expanded the idea into, what he called "neoclassical theory" which was supposed to be a conceptually clean alternative to quantum electrodynamics. But then, as with Schrodinger, a computational mistake in attempts to replicate QED predictions (after severa successful examples) sidelined the "neoclassical theory."
In mid 1980s, A. O. Barut found and fixed that error, and developed it into "self-field theory" with an impressive volume of work (helped along by several younger collaborators) and replicated many QED results, including the higher order radiative corrections, as far as they could compute them and beyond any experimental accuracy at the time. Thus they did demonstrate that as far as the agreement with the major experiments, QED had no advantages over the self-fields.
Conceptually, of course, the self-fields were far cleaner theory -- just the coupled interacting (and self-interacting) classical matter fields and EM fields, with no orthodox QM absurdities or QED divergencies. In principle the model was capable producing the mass of electron (or the fine structure constant) from the first principles, and they did manage to get some relatively crude soliton-like solutions and electron mass approximations (the nonlinear partial differential equations involved were very difficult, even by todays standards).
Barut's group also failed to demonstrate the equivalence of the self-fields to the predictions of QED to all perturbative orders. Then A. O. Barut died in early 1990s, and the group lost its track, each of the younger guys went their own way.
There are still some Russian and Ukrainian physicsts pecking at the variations of the Barut's self-fields (such as Oleinik, who claims to have obtained good approximation for electron mass from it), but it hasn't overall moved very much since the Barut's death. Jaynes, who inspired by Barut's results, went back to rework his "neoclassical theory," also died recently, so that work is left orphanned, too.
Another class of theories was spawned from the Nelson's stochastic formulation of QM from 1960s, which from stochastic mechanics grew into electrodynamics, named Stochastic Electrodynamics (SED). Marshall and Santos group has in recent years developed furhter a subfield of SED dealing exclusively with quantum optics problems, they call their model Stochastic Optics [SO]. The SO has reproduced the experimental results of all the major PDC based experiments of recent years for testing Bell inequalities or demonstrating other "non-classical" properties of photons.
The SED/SO use classical EM theory supplanted by the random background EM field (Zero Point Field) and classical point particles for the charged particles (or, in some variants, the Schrodinger eqation, with the external EM field approximation, i.e. without the self-interaction). Although more effective in producing the final results than Barut's self-fields, the two theories can be seen as one fundamental theory (the self-fields) and its computationally more practical (external EM field type) approximation, the SED, where SED simulates the complicated self-fields via the stochastic EM background and the soliton solutions of the self-field with point particles in this stochastic EM field. In the last couple years, Marshall has moved toward expanding SED toward extended particles and their stochastic fields, while retaining the stochastic EM background. Whether that will improve SED so that it can replicate more of QED predictions (beyond the quantum optics, where SO works quite well), it is not clear at present.
There have been several other more exotic variations among the alternatives to QM/QED in recent couple decades, but I think we are reaching the practical limits of the slashdot's message board scheme, so I'll leave it for some other occasion. Thanks for the nice discussion. You can have the last word in this thread, if you wish.
(Notice that this doesn't say anything about which theories are "reasonable" or not). It can be
shown that certain inequalities must be satisfied by any physical theories of this type.
That is a correct -- the inequality doesn't exclude any LHV theory a priori. But when the experimental results are being adjusted, to match the so-called "ideal QM prediction" ("ideal" is an euphemism meaning that it doesn't actually predict the data correctly), the additional assumptions, claimed by their advocates to be "reasonable," are introduced which all by themselves exclude the whole classes of HLV theories (for not complying with these "resonable" additional requirements). So that is how the "resonable" HLV constraint comes into the play here.
It is a question open to experiment whether nature violates Bell's inequalities. We seem unable to agree on whether Bell violations have been measured.
It is not a question at all, for anyone with some knowledge of the subject, whether any actual experimental data so far had violated Bell inequalites. None ever did. Not a single experiment had such data.
What violated the inequalities in all experiments making such claims are the adjusted data, the data filtered out and modified based on some arbitrary and unprovable assumptions. Consequently what the experiments exclude is not an arbitrary LHV theory, but only a subset of LHV theories which, not only reproduces the measured results (and some do so quite well), but also complies with those ad hoc assumptions (which come from no basic postulate or experimental results; after all, they are put in by hand precisely because they don't follow from anything else).
If they have been then locally real theories are wrong (not that quantum mechanics is right). If they weren't violated when they should have been, then quantum mechanics is wrong. There aren't any other choices.
The sticky part is "when they should have been." Namely, if you have a theory which supposedly corresponds to reality (as far as experiments can establish), say QM, then the results of Bell inequality tests should match this QM prediction. They don't. But that doesn't mean QM is wrong.
Specifically, the Bell's QM "predicition" showing that QM ought to violate his inequality is very sketchy, back of the envelope style, which ignores many additional effects in any real experiments. So it is no wonder that such "prediction" doesn't match the data. It is not a real prediction but a sketch, a hint for someone to do the full calculation, taking into account all the effects involved in a real phenomenon (i.e. it should be a full Quantum Electrodynamics [QED] calculation, not the little skeletal calculation of the Bell's paper).
If anyone had ever made the full QED calculation of any Bell inequality experiments, the prediction of such full calculation would match the obtained data, no one on either side doubts that. (The non-relativistic QM is not suitable for such prediction, except as a rough indicator of qualitative behaviours.)
In other words, the full and exact quantum electrodynamics prediction, capable of predicting the actual data (the average photo-detector counts obtained), does not violate Bell inequalities in any of the set-ups tried so far.
The only thing which has ever violated the inequalities is the "ideal QM prediction" which is the prediction Bell sketched in his papers (deduced using orthodox QM collapse interpretation), and which doesn't match any actual experimental data.
And, obviously, any synthetic "data" (the data obtained from the actual data via ad hoc adjustments and filtering to match the "ideal QM prediction") will violate the inequality.
Therefore there is not a single known experimental setup to date for which the full quantum theory (QED) prediction would violate the Bell inequalities. Namely, if there were such set-up, since the full QED prediction would predict the actual data correctly (it would have computed detector efficiency and noise levels), we would have had already a loophole free test.
It is unfortunate how the ideological zealotry in this field, the desire to uphold the orthodox QM interpretation with its collapse at all costs, has distorted the normal scientifc procedure. Normally, when you get data that don't match the theoretical prediciton based on the initial model (the Bell's sketchy QM calculation), one would try to refine the model, include additional effects which may have been overlooked in the initial model, and see if that agrees with the experiment better. Additionally, an experimental setup would be modified to control better any unforseen and undesired effects.
But in this unique case, contrary to all common scientific practice, instead of refining the model, the data already obtained gets subjected to additional substantial alterations, rationalized by ad hoc, unfounded and unverifiable, conjectures, to bring them into agreement with the sketchy, incomplete model (the so-called "ideal QM prediction" as sketched by Bell). And all that trouble only to avoid disturbing, or even casting doubts on, the orthodox version of collapse used in the essential way to obtain that so-called "QM prediction."
If somehow the Bell inequality tests are not so charged with emotions and high stakes, if they were just some result in an obscure paper that nobody cared much about, and that a professor had assigned to a graduate student to test experimentally, and if the student, having obtained the results and having noticed they don't match the predictions of initial crude model, had decided to keep the model anyway (figuring it is too much trouble to work out a more realistic one), and instead chose to modify the obtained data to fit the crude model, rationalizing that he is only making "reasonable" (at least to his and his family's personal satisfaction) assumptions and adjustements --- well, that student would likely get thrown out of the school for research fraud (these things have happened).
Alternatively, say you took a group of physics students, educated them for several year in such a way that they never had any access to Bell inequality, hidden variables or the related controversies. At the end you give them the setup used in Bell inequality tests and ask them to obtain results of coincidences and come up with QM/QED model describing the situation. Not in a million years would any of them just come up with the kind of convoluted reasoning and rationalizations to tweak the data you see in the actual papers on these tests. They would obtain the same data everyone else obtains (but they wouldn't know it would be desirable if the data could violate the Bell's inequality), they would work out the QED model which, if you had picked the batch of the brightest, would match to a reasonable degree the data obtained. And neither data nor the QM/QED prediction would violate inequalities, and they would be perfectly happy.
It takes years of conditioning into the particular absurd twists and turns and leaps of logic at the just right places of these kind of experiments and their analysis, to ease someone into "cheating" on the Bell tests and not feeling any guilt or even being aware they're doing it. All the dubious leaps, which would normally raise red flags in a mind of any rational person, have been drilled into the fully automated operation, into habits devoid of any thought or doubt.
It is true that the predictions of quantum mechanics violate Bell's inequality (that's why Bell's inequality is interesting).
Well, as explained above, that is not true. A real quantitive QM prediction, the kind you can compare its figures with the experimental data and obtain a good match, requires a massive calculation specific to a given experimental setup (including the full initial and boundary conditions, to solve the partial differential equations and inclusion of effects of all dynamical laws involved). And if the QM is correct and the model of the experimental setup is properly constructed, the QM prediction ought to match the data obtained. And since data obtained in any set-up to date had never violated the Bell inequalities, not even remotely, that means that the so-called "QM prediction" which violates the inequalities, isn't a real prediction at all, but a glorified thought experiment supplanted by a bit of "back of the envelope" sketch of QM-like calculation, useful at best for qualitative or heuristic purposes, but of no much use for the quantitative predictions of this phenomenon.
While the quantum mechanical explanation of Bell violations relies of the collapse postulate, of course, this has nothing to do with the empirical question of whether Bell violations occur in nature.
You are objecting to the part one of my message. The connection you are talking about is the essence of the part two of my response. In brief:
a) If the empirical tests cannot show (loophole free) the violation of Bell inequalities, that implies there is no justification or need for the orthodox version of collapse and the rest of its "measurement theory." The collapse, to the degree it occurs, would then be a consequence of some underlying (local, nonlinear) dynamics, like some type of phase transition.
b) If the empirical tests do show (loophole free) the violation of Bell inequalities, then any underlying local dynamics (local realism) is excluded. That still doesn't mean the orthodox interpreation or its version of collapse is valid, it merely prolongs its viability since no good alternative is available.
Thus the empirical (loophole free) confirmation of the Bell inequality violation is the only thing which would uphold (and not very convincingly, at that) the orthodox version of the collapse.
The Bell's theorem as a theoretical reuslt is what had placed the same question [i.e. is there any need for orthodox "mesurement theory" at all (including its state collapse)] in a testable form, giving thus the orthodox interpretation the lease on life pending the definite experimental results. Following the fall of von Neumann's and Kochen-Specker theorems (as proofs of impossibility of any hidden variables consistent with QM predictions), the orthodox interpretation had no reason to exist, no reason for its version of wave function collapse, since everything could, at least in principle, understood as a result of some, presently unknown, underlying dynamics.
The above shows how the Bell's inequalities and their empirical tests (if case (b) occurs) support the orthodox interpretation and its version of collapse.
The other side of this coin is that the theoretical Bell's inequalities rely on the orthodox interpretation of collapse to deduce its QM predicion (which sets LHV boundary in the inequality). So the boundary in the inequalities depends on the Orthodox form of collapse.
Now, it turns out the experimental data don't violate the inequality. Normal scientific method would in that case be to work out a more accurate QM model (to replace the QM side of Bell's inequality) which can replicate the actual data as it was measured. After all, the detector's efficiency (or the background "noise") isn't some god given untouchable and unspeakable decree, but it is one of the physical/QM properties of the experimenal system.
Instead, the orthodox school had merely renamed the Bell's QM prediction as "ideal QM prediction" and then gone out their way to fix the "non-ideal" experimental data, based on several unverifiable ad hoc assumptions, which are outside of the postulates and which almost by definition exclude LHVs all by themselves (with no tests needed, e.g. the "fair sampling" is directly contradictory to what one would expect from almost any LHV - that the particle detection does depend on LHVs [what else could it depend on but HVs, anyway] - the "fair sampling" imposes upfront the condition which excludes any LHV theory with such dependence.)
You seem unconvinced that they have been measured, and I can respect this position to the extent that there are genuine flaws in the experiments.
What I am saying about the tests is not a matter of convictions or tastes at all. What the test have excluded is not all LHVs but the LHVs which satisfy not only the normal requirement to be able to replicate the experimental data (or equivalently, to replicate the exact, not just "ideal," QM predicitons, which of course ought to agree with the actual data, as well) the additional assumptions applied to the experimental data to bring them into agreement with the "ideal QM predictions" of Bell's inequalities.
The only thing which is a matter of tastes or convictions is whether these additional assumptions are "plausible" or "reasonable" constraints on LHVs. But there is no dispute at all whether these additional assumpitions are being made -- anyone with any knowledge in the subject knows they are being made.
Now, to see whether these additional constraints on LHV are actually plausible and reasonable, one has too look at a variety of proposed LHVs which can replicate the experimental data of those tests and check whether they satisfy these additional constraints.
If you check the literature (especially those from the Trevor Marshall, Emilio Santos and their school) you will see that those additional, innocently sounding, contraints are preposterous -- they exclude reasonable theories (such as Sotochastic Electrodynamics [SED] and Stochastic Optics [SO]) upfront, with no experiment needed. The SED/SO does in fact replicate the data from all the PDC photon experiments for Bell inequalities and for the other so called non-classical effects in quantum optics. To exclude such broad types of theories upfront based solely on what someone wishfully labels "fair sampling" or "non-enhancement" hypothesis, is absurd. At the very least such theories demonstrate plainly that those euphemistically labeled assumptions are throwing out, all by themselves (with no experiment needed to support them) much more than what is usually claimed to be excluded a priori (i.e. by the added assumptions alone).
I completely agree with your remarks concerning the projection postulate, yet I somehow fail to see the relevance for tests of Bell's inequalities.
The two are inseparably entangled, as it were. If one falls the other goes, too.
First, it is precisely the subsystem state collapse, as prescribed by the orthodox interpretation, how the Bell's (or EPR-Bohm) theorem deduces the quantum prediction side of the Bell's inequality. (And this is the same collapse that quantum "computers" are supposed to use to extract their "computation" results out of the entangled states; which is what brought us here.)
Second, as explained in the previous message, the Bell tests were the culmination of a long debate whether the hidden variables are excluded by QM (or its predictions). First there was von Nemann's proof (from 1928), which claimed to prove HVs are inconsistent with QM predictions. That was accepted by the mainstream as the final word, which in turn gave rise to the present form of the measurement problem -- if HVs are impossible, then the statistical nature of QM cannot be due to unknown or uncontrolled values of some hidden variables, being merely revealed by a measurement.
The linearity of the evolution equations of QM precluded the combined system, the "measured system" + the "measuring aparatus" from ever being able to chose or settle into one of possible results. Von Neumann's "solutions" was to declare that it was human mind, the mind of the observer which finally made such decision (this view was also promoted by Wigner).
That was a clear acknowledgment that there is no way the rules of the evolution along with his interpretation of them, especially his no-go theorem on HVs, can reproduce what happens in a measurement -- the system, in real world, does seem to pick somehow one among the alternatives as the measurement result, i.e. it appears as if the state got projected onto the one definite aparatus state (eigenvector).
Others, who didn't like the idea of "human mind" becoming a part of a physical theory, but who bought into the von Nemann's no-go theorem for HVs, kludged from the two contradictory pieces, what nowdays is called the orthodox interpretation. Since the two ways of evolution contradict each other, we will give each a role but never at the same time. How this is to be decided, which one is in charge and when and where it is supposed to switch the rules, that was never really explained. But too keep the physics students from asking too many questions, they wrapped the kludge into the term "measurement" and wrapped all that into the generous layers of warm and fuzzy talk about "irreversibility" "macroscopic aparatus" etc.
Not everyone bought it, of course. One who didn't buy either, the von Nemann theorem or the "measurement" fog, David Bohm went out and constructed an explicit HV theory reproducing the QM prediciton -- in effect showing that von Neumann theorem was wrong.
Well, that meant there was no need any more for all the "measurement" fairy tales, for the two sets of rules and a divine intervention (or a mind), to switch between them. The orthodox school didn't give in though -- all those multitudes of leared tomes and deep papers they produced to "splain" it all, to the simple-minded physics students, who stubbornly clung to their common sense -- all that work down the tubes. No way. All those deep thoughts on complementarity and marvelous connections with the hindu worldview, to dump it all. We can't let that happen.
In the scramble that followed Bohm's theory, the orthodox school kludged quckly another proof, Kochen-Specker theorem. It backed off a bit from the von Nemann's grand claim that no hidden variables of any kind are possible, to a lesser claim that "no non-contextual hidden variables are possible." And since the non-contextual kind was declared good and the contextual kind was declared to be a no-no, everything seemed to be now back where it was before Bohm. The Bohm's HVs were "contextual" hence no good, hence ignore them, shut the Bohm up. Bohm squeeled for a while, but what could he do, everyone's got to eat at the end.
No major objections to Kochen-Specker were allowed into the open for several years, the wavering orthodox line was held, until John Bell published his paper showing (what Bohm and everyone else who cared about the whole mess, already knew) that the Kochen Specker theorem suffered essentially the same flaw as von Neumann's, so it is no good. But since Bell had another proof in his paper, the Kochen Specker fell, the Bell inequalites arrived. They did retrench a bit from Kochen-Specker, but better something than nothing, since Kochen-Specker could not have been held for much longer, anyway.
The core claim of Bell inequalities is that if QM predictions are correct any hidden variables which reproduce these predictions must be non-local. And since non-local is "bad," then no "good" hidden variable theory can exist. And thus the whole mass of learned production from the best and sharpest minds of the orthodox school on the mysteries of the quantum "measurement" is still a valuable contribution to science and a required reading for the poor and stubborn physics students.
So the Bell's inequalities are the last defense line upholding the whole orthodox interpetation -- they provide a need for its existence. Namely, if a local hidden variable theory could reproduce the QM predictions (which Bell's theorem prohibits), then as with the fall of von Neumann's therem, there would be no need for the measurement theory mistique, collapse and the rest. Everything would revert back to common sense, measurement simply reveals the values some variables had at the time of measurement. No need to write "learned" tracts on reconciling and understanding the contradictory or for invoking hindu deities to arbitrate between the two contradictory set of rules.
At the same time, as pointed out at the top, Bell's theorem uses, none other, but orthodox interpretation of collapse to deduce what the QM prediction ought to be. So, it is a mutually supporting arrangement, between the Bell's theorem and the measurement theory of the orthodox interpretation -- if one falls, the other has to go. Well, one must admit it was cleverly crafted. But the nature (un)fortunately is the last judge what ought to happen. The actual data from the experiments showed no violation of Bell's inequalities. What to do now?
Well, the clever folks who fought off valiantly the great Einstein himself, then the scary Bohm's assualt, surely won't fold their wares just for some little experimental data. So the Quantum side of the Bell's inequality (the supposed QM prediction based on the orthodox interpretation of subsystem collapse, which violates inequality, but doesn't match the actual measured data) was relabeled "ideal QM prediction" and the experimental data, by implication, as non-ideal, thus in need of fixin', requiring the massive hand adjustments of the obtained data points, rationalized by a variety of unverifiable assumptions pulled with a lots of handwaving out of a magicians hat ("massive" as in changing or injecting 990+ points on of every 1000 presented as the final all nice and fixed-up result).
Ain't that so convenient. Instead of, as anyone with an ounce of common sense would suggest, producing the correct QM prediction and comparing that to the experimental data, the alleged QM prediction of the Bell inequality is kept as is (since otherwise, of course, there would be no inequality for the correct prediction, the one that matches the actual data -- hence no Bell theorem, hence the last defense line of the orthodox dogma would fall) and the experimental data is wishfully twisted around to bring it into compliance with this alleged QM prediction.
Unfortunately, a poor physics student taking courses in QM has no chance of disentangling this ball of tangled up nonsense which has come to resemble talmudic law or some such endless web of legalistic word games.
The new line of defense (to become effective as soon as a confusing enough theorem can be put together), is going to be "decoherence" (an euphemism for incoherence, I guess). That is when the "quantum entanglement" (another very appropriate name) will be quietly dropped.
NOTE: I am not suggesting above that someone actually set down and plotted out all the twists and turns of the developments described. No need for that. It is the phenomenon of the same kind as the Adam Smith's "invisible hand" guiding the economic developments as if they were cleverly planned, even though there is no explicit plan and every player is merely pursuing their own narrow self-interest. Science does operate as a marketplace of ideas and models.
And I did not make up the numbers (though I did get the reference wrong). See: C.A. Sackett,
et. al, "Experimental Entanglement of Four Particles" Nature 404 (2000).
Well, that's a different topic. All they did is create an entangled state (which is the type of state serving as an input into the Bell inequality tests). Even the classical Maxwell equations allow for entangled EM wave packets of the same form. From theoretical viewpoint they're just one form of initial & boundary conditions, there is no controversy about it at all. The classical entangled EM wave packets do not violate Bell inequality. (And neither do the quantum ones, as far as anyone could measure to date.)
A computer built on such 'classical entanglement' would be merely an analog computer, having no special powers. And neither would QC, unless one can establish the additional very special properties of that state, the subsystem collapse which the Bell inequality experiments were devised to test.
The paper doesn't even try to prove that those states exhibit the subsystem state collapse property, which is the point of Bell inequality tests. It only deals with preparing particular initial & boundary conditions, which is fine (and probably useful), but not relevant for the subsystem collapse hypothesis or the Bell tests of it (which in turn is the only way the QC could read off the results of the "computation").
I agree that we have not yet seen a perfect Bell inequality test, but the position you seem to be taking is that quantum mechanical non-locality cannot exist and that there must be a flaw in any experiment that purports to detect it.
The common interpretation of Bell inequlity tests is merely another manifestation of the problems which were part of QM since the projection postulate (or wave function collapse) was introduced in 1920s. The EPR phenomenon was application of the projection postulate to the subsystem, in order to show how absurt it is. Bell's inequality came in 1960s (and tests in 1970s), when QM was already four decades old.
Einstein and Schrodinger who were among the handful key founders of QM did not accept the wave function collapse from the start. It was absurd, an ugly kludge trying to hastily patch up the holes in, what at at the time was, immature new theory, to make it appear complete.
The core absurdity of the projection postulate is that it switches the rules of how the system evolves midstream -- suspends them at an undefined moment in time, based on no objective criteria, for undefined length of time, then changes the state of the system in a way cotradicting the original equations (which were "luckily" now suspended, otherwise there is a contradiction), then the new rules suddenly go away, at some undefined time and for no rime and reason, and the old rules are said to hold again.
It is one ugly kludge devised to patch up the contradiction between dynamical equations and the presumed effect of measurement -- since you can't have two contradictory rules in a theory, the "solution" was to effectively inject divine will into the game and have it willfully switch the rules midstream back and forth, as it pleases.
The Bell's inequalities were devised (by late John Bell) to serve an experimental test which would decide whether this switching of the rules is really necessary -- whether there may exist a single set of "reasonable" rules (i.e. without instant action at a distance), which always hold, which need no divine intervention to suspend them and then let them work.
The way I see the experimental results so far is that indeed the test does show that the existence of a single set of rules is consistent with the experimental data. Only when the proponents of the divine intervention (the collapse kludge), sticking with that style, I guess, inject yet more divine intervention, the arbitrary hand-put assumptions (which are outside of the postulates of QM agreed upon upfront), which conveniently let them weed out (or inject new ones) the data points after they have them already at hand -- only then these hand-tweaked "improved" data excludes the possibility of the single set of rules. Well, who would have guessed that.
So, ignoring the euphemisms and other verbal gimmickry (e.g. talking about "loophole free proof" instead of "proof that actually works" or "proof that proves" or just "proof") and silly little games with data after the "bad news" are in -- the nature, as far as it has revealed itself until now, seems to be perfectly happy in using single set of reasonable rules. The rules we don't know as yet, but which are not excluded by any facts known to date.
The experiments I was referring to did not use entangled photon states, they used entangled
ion states.
The ion based tests open their own set of loopholes, while closing the common photon tests loopholes.
Unlike photons, ions can be detected with high efficiency (theoretically 100% since they're massive particles). But since the spin coupling energy (with Stern-Gerlach magnets, the analogue of polarizers in optical experiments) is much lower than their kinteic energy, the spin measurements (selection) are much less reliable than those of optical photon polarizers. This results in large background counts (due to depolarization) and this subtraction is a well known loophole for LHV models (also occuring with photon tests when the sensitivity of the detectors is increased).
Additional problem is in reliable production of the entangled pair state, again due to the low energy of spin-spin coupling (between the spins of the ion pair) relative to other energies involved in the process of pair production and collimation. The result is again a large number of "accidental coincidence" detections, i.e. another contribution to the background to be subtracted.
Hence the background subtractions make ionic tests very similar to the case of photon tests when the photo-detection is increased to near 100%. This can be achieved by using very high energy photons (e.g. gamma photons from the electron-positron annihilation), in which case one can have near perfect detection, but polarization measurement doesn't work too well (via Compton scattering), producing very large background which needs to be subtracted (exactly as with ions, and for essentially the same reason).
An alternative way to increase the photo-detection efficiency is to use very sensitive (low threshold) detector, but that produces large dark current, the background noise, which again has to be subtracted. The resulting unsubtracted data in such case are almost exactly what a classically entangled EM wave packet would produce (i.e. what Maxwell equations would predict). You can, for example, see the actual raw data from Asepect's PhD thesis, where he did his famous cascade experiments, on Caroline Thompson's web site. For more modern PDC based experiments, see the similar Stochastic Electrodynamics models (which are again the Maxwell equations based models, but with stochastic initial & boundary conditions) which reproduce the raw data for these experiments, on the Trevor Marshall's site.
It is true, as far as I know, that no single experiment has gotten sufficient sensitivity using spacelike separated measurements... yet. It seems somehow perverse though to hang a defense of local realism on this fact.
This is the oldest handwaving argument for dismissing the loopholes in Bell tests, i.e. why would some future increased sensitivity (for detection or polarizer efficiency) suddenly switch from the good agreement with QM (modulo loopholes) and give preference to the local realism.
First one should note that the non-adjusted experimental data is already consistent with the local realism (and there are numerous local models for variety of the setups reproducingt he experimental non-adjusted data). So nothing here has to change for more sensitive experiments. Only the wishfully adjusted data (when the loopholes are dismissed via ad hoc unverifiable assumptions) exclude local realism.
Second, it is perfectly natural for any local realistic model to make the efficiency of the detector or polarizer dependent on the values of the local (hidden) variables. Such dependency is outright excluded by the fair sampling (be it sampling by the detectors or the polarizers; in the ion case the critical fair sampling problem is at the Stern Gerlach magnets, the "polarizer," not the detector, which is here near-perfectly efficient; while in photon case it is at the photo-detectors, and not at the near-perfect polarizers). The ion tests only shift the fair sampling (in the hidden variable space) problem closer to the source, at the Stern-Gerlach and the pair source production depolarizations (which results in the background counts, which is presumed to be a fair sample in the LHV space, thus it is flatly subtracted subtracted from the total counts).
To illustrate this point in a form more accessible to non-physicists here, consider a national poll using email. Such poll will fail to detect people who do not have computers with internet connection and email account. Suppose now the poll analysis expert wasn't informed about the method of communication used to obtain the poll data. This is analogous to the Bell test experimenter looking at the counts of particles detected, but not being able to measure or know anything about the so-called local hidden variables (analog to the email, which is here invisible variable/value to the poll analyst).
The analyst, not knowing anything about the underlying means of communication, proclaims now that he will assume that the chance of being detected by the pollster doesn't depend on the (invisible to him) method of communication, hence the sampling is proclaimed to be fair, by declaring it to be so. This is exactly how the experimenters in the Bell tests establish that their sampling is fair (at detectors or polarizers), independent of the hidden variables -- by proclaiming it to be so.
Now suppose in our poll, a question asked "what was your income?" Clearly, the sample is biased here, and the income discovered this way will be higher than the national average. In other words, the poll is more sensitive in "detecting" higher income than lower income people. In the extreme, if the question is "are you homeless," the sample will completely miss any homeless person, i.e. this "detector" is made completely insensitive to the "homelessness" by virtue of the particluar value of the hidden variable (the means of communication = email). OTOH, if the means of communication were walking through the parks at 10PM, and asking anyone encountered the same questions, the results would be biased the other way. Here the hidden variable "means of communication" = "asking people in the parks at 10PM" -- the variable has different value, and the detection profile is quite different.
In other words, the hidden variables will perfectly naturally bias the sample, almost by necessity, since they do affect (or are correlated with) what is detected and what is missed. Ruling out the sample bias by fiat (as is done in every Bell test), is effectively excluding the hidden variables upfront, by declaring it so.
The phenomenon you point out has been called the unreasonable effectivness of mathematics in natural sciences by the great physicist Eugene Wigner. At the turn of the last century, some pure mathematicians were half-jokingly bragging that they are working in group theory, since it is so abstract and pure discipline, it could never have any conceivable application and thus it can be kept unspoiled by practical compromises, and can be enjoyed just for its beauty. It was only couple decades later that none other but Wigner had discovered great usefulness of the group theory in quantum physics. So, yes, that has happened over and over throughout the history of science.
The issue with QC is that it is advertising itself as a physical theory, and even being promoted as an applied physics or enineering based on a dubious and unverified link with the reality.
Of course, there is nothing wrong in scientific conjectures, as long as they're being labeled as such, with clear and honestly acknowledged distinctions between the facts and the hypotheses.
In case of QC, the weak hypothesis at the root of that theory is labeled as a fact (the subsystem state collapse, necessary to read off the results of the "computation").
Even worse, the legitimate critics, including some reputable physicsts with many years of publishing well received and cited works, end up getting gagged by the peer review "priesthood" (as Trevor Marshall, one of such critics, calls them), their research grants somehow dry out, as soon as they point out that emperor has no clothes, that there is a rot in the core this hyped-up discipline.
Bell's inequality has been tested with entangled ions with nearly 99% detection efficiency (from the same group at Rice who demonstarted 4 particle entaglemnet in Science). Bell violations are real. Deal with it.
Sure, and I got a nice bridge I could sell you, real cheap.
The detector efficiency alone on the photon wavelenghts normally used won't get you beyond 60%, if you wish to take huge noise, 30% and up depending on wavelengths (which in turn requires background subtractions, invalidating the experiment as a "loophole free" Bell inequality test, ie. it fails to exclude the local hidden parameters).
But if you reduce the detector trigger thresholds (such as using ultra-low noise low temperature photo-multipliers), to reduce the noise down to 1-2 percent, the sensitivity, hence the detection efficiency, drops down to 20% or below. It is a no win tradeoff, you either get noise or you get low sensitivity, invalidating in both cases the "loophole free" status for the experiment.
The parametric down conversion (PDC) sources used nowdays also give outright 50% loss, making them entirely unsuitable for the loophole free test. Of course, if you accept additional hand-put assumptions (which are unverifiable and which are outside of the QM postulates), you can handwave it as unimportant.
One try to improve detection efficiency, without noise, by going to higher frequency photons, but that has a downside in decreasing the polarizer effectiveness (depolarization increases). Thus for the ultra-high frequency photons, such gamma photons, which can be detected at near perfect efficiency, the optical polarizers don't work at all, and one has to use Compton effect to obtain very low power effective polarizer (these tests have been done, too, but are of much worse quality than those with the optical photons).
Then you get aperture and geometric losses, which often exceed all other (small aperture is often chosen to avoid noise, reflected photons and accidental coincidences from the multiple sources). Again, these can be adjusted away via yet another hand-put assumption.
To test Bell inequalities in a loophole free experiment, none of these adjustments on the raw data may be done, and the net efficiency on the raw data has to be over 82%.
The grant savvy experimenters have in recent years gotten into habit performing several adjustments implicitly (usually embedded into the software operating the setup) and then quoting as their setup "efficiency" the figures of some minor hand adjustments done at the end (such as polarizer losses), ignoring to mention the extensive data "cleanup" done by the software. That kind of gimmick may be fine for engineering aplication, but has no bearing on the Bell inequality tests.
The only thing which could remotely come close to 99% (if you haven't made the figure up, as it seems likely) would be if someone had "assumed away" all other adjustments, except for the depolarization, which may be brought to 1-2% in losses (for optical photons and if the aperture is made very small; of course, then the aperture losses become quite large, well over 80% losses just from that).
If anyone tells you they have made a "loophole free" Bell inequality test, they're trying to be humorous or are flatly lying. Since nothing is even remotely close to it and anyone even casually informed in the field knows it perfectly well. It would be like someone telling you in confidence to run and buy Intel stock, since they have a new Pentium prototype running at 500 GHz. You would know right off it ain't so. With or without adding the beowulf cluster.
You could be saying the same thing about aeroplanes.
Research and experimentation are rarely a waste of effort, whether to prove or disprove, because we
have to find out. The skeptics said we would never build aircraft, split the atom, travel safely in railway
carriages, go to the moon, etc etc etc.
The key difference from your analogy is that in your examples, the skeptics were the establishment physics, the folks who decide what is published and what gets funded, while the people claiming something is possible were the outsiders to the establishment.
In the case of QC and quantum entanglement, it is the establishment which claims something is possible while the heretics claim it isn't. So, the much closer analogy is the case of medieval church, an establishment of that era, claiming various superstitions and miracles are possible, while skeptical heretics (such as Galileo or Bruno), who were outside the establishment, claimed that was bunch of bunk.
According to many other physicists quantum entanglement does occur, and there is supporting
experimental evidence. This evidence is disputed by some people, however the majority accept it as valid.
Any experimenter who did such experiments (and there were dozens of experiments over the last 3 decades) will acknowledge that the experiment was not "loophole free," which is a euphemism for "the actual data didn't confirm it, but if I assume certain statistical properties of the photons that escaped detection (and which, luckily, no one could now show to have been one way or the other), and then remove the data points which don't fit such assumption, and also fill in the gaps for the missing points (which just happen to make up 995 out of 1000 final data points) with the points having the assumed statistics, then the statistics of these new and improved data points does violate Bell inequalities, proving thus the quantum entanglement." That's what it comes down to, when you peel of the jargon, the handwaving and the euphemisms.
Go to the Los Alamos preprint archive (I gave the link earlier), pull the emails of the authors claiming such verifications and ask them whether their experiment was "loophole free" (none was) and when is the "loophole free" version scheduled to start (not scheduled, not designed, not within present detector technology).
A quick search of the Physical Review Letters web site shows 20+ letters in the last five years alone deomonstrating the preparation of entangled quantum states in the laboratory.
Preparing desired state, while often technically challenging, is not the weak point of the QC. Reading the results of the "computation" is where the scheme will turn out a dud. See my other comments in this sub-thread on why that is so.
I'm curious what motivates your objection to quantum mechanics. Do you reject the mathematical theory of quantum mechanics (in all of its various guises) which has held up rather well to experimental validation, or is it instead that the heuristic, post-Copenhagen interpretation of the theory (i.e. "spooky action at a distance") rubs you the wrong way?
My objection (and Einstein's, too, among others) is against the branch of QM which grew out of the state collapse postulate (that "fruits" of which include QC and quantum teleportation). That is a postulate independent of the rest of the postulates (the ones that successes of QM rest on), it has no practical or explanatory power.
It is a parasitic useless add-on on which the assorted swindlers have been triving for decades, ranging from the fast-talkers among physicists pulling the fast one on the hi-tech execs and VCs to the the new age gurus on "quantum healing" ripping off little old ladies with bad joints and wide eyed teenagers looking for "self" and its meaning (there ain't one, if you don't mind me spoiling the plot).
The relation of this postulate to the rest of QM is that of a loser exploiting and taking credit for his older brother's good reputation and success.
Caroline is an outsider to the field, but otherwise an intelligent person and specialist in her own field (statitstics), which has great deal of bearing on the interpretation of Bell inequality tests. While I certainly don't buy all of her skepticism, and even less her conjectures about the alternatives, she does have a very sharp eye to spot a swindle, a loophole in setup and the argument. Also, as an outsider, she does present the key issues in a much more accessible way to non-physicists, without skipping over or hiding the tricky points (as popular books by physicsts tend to do).
Not upon the part of QM discussed here. The quantum state collapse (in particular the subsystem state collapse), on which the QC's connectin with reality vitally depends on (to read off the results of the so-called "computation"), that is a separate, independent from the rest of QM, postulate (basic assumption taken for granted). It is a gratuitous add on, with no experimental or explanatory (of observed phenomena) consequences.
To separate that postulate from more plausible alternatives (such as "incompleteness of QM," i.e. the existence of additional quantities for which the rest of QM gives only statistical, but individual, predictions), Bell inequalities were devised (by late John Bell), which give a cutoff point on statistical correlations in a special type of multipoint photon/particle detections. If the counts violate the inequality, the "local [hidden, unknown] variables" are exluded as a possible explanation of these experiments. If the counts don't violate the inequality, some underlying [unknown] quantities are consistent with the rest of QM.
It turns out that actual data doesn't come even close to violating the Bell inequalities. Only after great deal of handwaving, aiming to convince that certain conjecture about the statistical properties of the missing data (the instances when the photons failed to trigger detectors) ought to be accepted as plausible, only then they can "adjust" (change to a more desirable form) the data, and lo and behold, the new and imrpoved data miraculously violates the Bell inequalities.
The fact that very specilized experiments are needed to find out whether such subsystem collapse occurs at all (consequently whether QC can ever work, even in principle), ought to tell even non-specialists that the successes of QM have nothing to do with that postulate. It is a parasitic add-on, with no real use (other than parting the cash from the fools who fund the swindle).
Furthermore, quantum entanglement is not a requirement for these processes.
See my earlier comment on difference between general entanglement (which is a well established process) and quantum entanglement.
The element necessary in any form of quantum computing, which provides the ability to read out the "computation" result, is the quantum measurement postulate (also referred to as projection postulate or state collapse postulate). For any nontrivial "computation" QC uses its special case, the assumption that a measurement on one subsystem will collapse the state of the remaining subsystem (this is supposed to happen even without any interaction with the remaining subsystem, which could be miles away and physical field/force is needed to carry out this remote collapse).
That element is an independent postulate of the theory. Nothing in actual explanatory power of QM requires it, no great successes of QM (which include much of todays semiconductor technology, where quantum solid state theory, developed in 1950s, helped point the way and provide theoretical tools for the more practical experimental research later) over decades need it. All detector count results are computed using correlation functions (such as Glauber's multipoint correlations used in quantum optics to predict correlations among multiple photodector counts) which don't require any collapse. The collapse is a gratuitous and by itself useless in any explaining (of any observed phenomenon), a parasitic add-on to the theory.
It has no operational use other than in "explaining" the experiments trying to confirm it (and none of them did, unless you're willing to believe several additional quantitative assumptions, about the state of unmeasured and unmeasurable quantities, assumptions which are outside of the postualtes themselves). And of course, they're used in "predicting" the existence of quantum computing, quantum teleportation and other assorted miracles.
Any claim by experimenters to have demonstrated QC, if they're fully honest, will disclaim it the same way Bell inequality tests are disclaimed -- yes it was shown, provided we accept additional assumptions (which are outside of postulates themselves) about the missing (unmeasured and unmeasurable) data. Only the so adjusted "data" exhibit QC or violate Bell inequalites. The raw data (unadjusted detector counts) show no such phenomena. These adjustements are sometimes expressed in terms of extrapolating the results to the sufficiently decoherence free state.
You seem to believe that reality is what you see.
Of course, not. I have been theoretical physicist long enough to know better (and I have been doing lots of other the after the academia to know even better than that). Reality, as far as physics is concerned, is the what the best underlying models say it is, which means it is subject to revision as the models are revised.
What that means is that there is "model," postulates, mathematical formulas and algorithms used to extract the behavior of the models. Model by itself is thus a pure construct. To make it mean anything there is also a set of "correspondence rules," prescribing how the properties of the model map into the observation. This is where the model makes the contact with conventional empirical reality. Without such contact it is not a scientific model, but a pure speculation (the artsy-fartsy stuff).
In modern physics the core components of "reality" of the model (strings, quarks, electrons) are never observable in any direct way. What is actually done is to compute some long chain of (mathematical) consequences of the model, then at the end of chain there is a set of numbers which can be associated, via the corrsespondence rules, with the experimental facts, e.g. with counts in some detectors. If the counts match the numbers produced by the model, and if one can vary the input assumptions of the model while still maintaining this match, well, the model is said to be "reality" behind the phenomenon. Now that doesn't exclude possibility of alternative. The present models of physics don't exclude alternative models. What experiments show is at best that a proposed model is consistent with the experimental facts, not that no other model can account for those facts.
The problem with QC model is that its vital contact with reality (without which the result of the "quantum computation" could not be read off) is that it relies on the state collapse postulate, which so far does not make sufficient difference by itself to be confirmed empirically, in the sense of exluding the common sense alternatives (such as allowing that QM is incomplete, i.e. there are variables missed by the quantum description, which only covers the statistical properties of such variables, but misses their detaled individual properties).
Despite 7 decades of experiments attempting to establish absence of those "hidden variables", including the 3 decades of Bell inequalities tests, no "loophole free" experiment exists as yet. The odd wording, "loophole free" experiment, is a customary euphemism trying to say in a nice way that no actual data in the experiments show what the experimenters wished to show (ultimately, the non-existence of local hidden variables, or specifically, the Bell inequalities violations). Only the fictitious "data," obtained via a very "special" kind of adjustments from the real data does violate the inequalities.
The justification for these adjustments is not the postulates of quantum theory themselves, but are ad hoc one shot assumptions about the unverifiable missing data, belonging to no theory, and useful for nothing else in physics but getting the otherwise "unwilling" data to fit the desired conclusion (violation of inequalities). If you don't accept them (as you don't have to, unless your funding proposal vitally depends on being able to bedazzle the fools with money), no violation follows, no QC (can't read the result of QC, it is still there, allegedly, but it can't be gotten to), no teleportation (and no funding).
Quantum mechanics is the current scientific dogma because it has successfully explained a _vast_ array of experiments.
Quantum mechanics, yes. But there is nothing ever measured explained by the quantum entanglement hypothesis. It has never even been confirmed experimentally (without loophole), much less that it has any use in explaining any phenomenon actually observed.
That hypothesis is based on an independent (from the rest of QM) postulate on how the composite system state transforms in the measurement. The actual postulate in fact contradicts the normal unfolding of a quantum state (as prescribed by the evolution operators, or Schrodinger equations), saying in effect that when the "quantum measurement" (never really defined with usable precision) is done, the regular dynamical equation somehow cease to be valid, for unspecified time interval, in an undefined way, the state "collapses," then somehow, at some, again undefined, point in time, the normal dynamical equations take over again.
It takes years of conditioning in physics to be able to submit ones common sense to such mind twisting "logic." And even then it never tastes quite right, there is always some fishy odor around it. It takes then more years to be able to snap out of it. But it can be done.
Eventually, of course, the peddlers of quantum magic will have to face the question -- where is the beef, show me the "Quantum Computer." Let's benchmark it. And when the proverbial rubber finally meets the road (which they've been skillfully avoiding for some years; read Kwiat's hedging with "extremely difficult"), the only thing which will collapse will be that whole house of cards.
Anyway, I know a number of folks who are working on various bits of QC research.
The actual Quantum Computing, if understood as a pure mathematical discipline, unrelated to physical reality or actual computing can be quite interesting (to those who enjoy that kind of abstract mind challenge). And it is not impossible that it may end up having some applications in analog computing (the plain classical style) if that can be made to work. Or inspire some neat devices based on quantum dots. One can always stumble into the right thing for the wrong reason. After all, Columbus thought he was going to India, and believed he found it.
These are not shady
scientists looking to push alternative theories under the rug and secure government grants on false
promises.
Well, that's true of most large scale swindles. Take various large scale superstitions (the religions) -- most priests will sincerely believe dogmas they preach. But try touching the core of the dogma, then you find out how it really works. The peer review in this field, for all major journals and commissions for research grants, is stacked extremely one sided way against anyone pointing to the fundamental flaw of the theory -- the vital experimental connection with reality of the whole QC superstructure is based purely on assumptions about the (iretrievably) missing data. If one makes different assumptions, as one is free to do about something which is unmeasurable, the whole relation of the QC with real world fizzles away.
Now, the old boy network running the peer review in all major physics journals, will let anyone challenge any detail of the superstructure, argue how fast QC will be, will some QC algorithm really work in n*log(n) time or some such. But try touching the vital "loophole," and you might have as well spit at the editors face or kicked the african killer-bee nest -- your manuscripts will be turned down with the lamest of excuses and run-arounds, your grant proposals flatly rejected. Just ask Trevor Marshall, who is quite a competent physicst, and has published many dozens of well cited papers (in other sub-fields) -- once he seriously poked into the "loophole" he couldn't get published in any of the major journals, or get funding for experimental refutation of the quantum entaglement, and ended up taking early retirment from his tenured position out of frustration with, what he came to call, the "priesthood."
Entanglement has a firm experimental footing as well as an fantastically strong theoretical basis.
There is a classical entanglement between regular EM waves, which is formally identical to the quantum state entanglement for photons (as appearing in Bell's inequalities). There is nothing mysterious about that meaning of "entanglement," everything is perfectly local, computers made using them have no special powers (beyond what an analog computer would have, if one could build a usable one). Dutch physicist Robert Spreeuw (well known name in the optics of atoms) had worked out quite far the mathematical correspondence between the two formally identical phenomena, including the extensions to the so-called "quantum computing." So, in that sense, the "entangled" state has been produced many times, in quantum or classical systems.
What separates the "quantum entanglement" is the presumed ability of quantum entangled state to collapse instantly the remote subsystem state when a measurement is done on the other subsystem. To test that key property, on which the Quantum Computing contact with reality vitally rests, Bell inequality (or its more recent variations) is used. And that is where no test to date has come even close to being "loophole free." While papers and preprints may not emphasize or even mention the loophole, the fatal loophole is present in every single experiment. Merely showing that the state is consistent with the entangled state (which is how far the actual, raw, non-adjusted data ever goes) doesn't prove that it has the key property of remote subsystem collapse.
To prove that, the raw data would have to be used, before any assumptions about the missing data (inferred to exist from the triggers of some, but not all necessary photo-detectors, and which is routinely pressumed to obey the "fair sampling" hypothesis) are used to adjust the raw data (raw detector counts). Additional data adjustments are also done, specific to the experimental setup (especially common are subtractions of background counts, again under unproven and unprovable assumptions about unmeasurables).
Only after all the adjustments, the wishfully massaged data does violate (amazingly enough) the Bell inequalities (which is the objective if one wishes to prove the existence of quantum entanglement).
Having been once a theoretical physicist (and having written masters thesis in this area), I had corresponded over years, via mail and email with most experimenters who had published the "almost" proofs of the quantum entaglement. And when pushed, yes every one will tell you that indeed, there is a loophole of one kind or another, the hand put assumption about the missing data which makes the adjusted data violate the Bell inequalities. Without it, on the raw data, none violates the Bell inequalities.
To put it in plain terms for the non-physicists here, one could for example, having no data on where you were 1 minute ago, assume that you were 1000 miles away from your current place. And, say, now we can all find you on your current place reading this message. We're missing the data on where you were 1 minute ago (and there are no outside witnesses to say one way or another) but with our 1000 mile assumption, that seems pretty amazing how you managed to travel that far in so short time. Now we take for granted that you did travel 1000 miles in 1 munute, and then we start constructing ever more marvelous hypothetical technology based on that enormous speed for an earthly vehicle. Sure, you could come up with some pretty nifty transportation systems if you build upon that 1000 miles/minute vehicle you supposedly must have used. And if someone is going to pay us to do research on these possibilities, we're not going to pursue seriously the issue whether our key unverified assumption (your location 1 minute ago) might be wrong.
That is what the issue in quantum entanglement comes down to. Without making the unverifiable assumptions of certain particular kind (like that you were 1000 miles away 1 minute ago) about the missing data, nothing unusual or amazing can be deduced, the entanglement measured on actual data is no different than the classical one (which of course, can't collapse instantly the remote subsystem state).
There've been some experiments in Italy (so no ref) that have been running over the past couple of years (not "the 1980's") that have "proved" entanglement over very large distances (kilometres)
You probably mean Geneva experiments by Tittel et al from 1998-99; check on the Los Alamos preprint archive for their 10 km exeperiments. There is the group's email address at the top of the abstract, go ask them if the experiments were loophole free (they were not). Now, of course, they'll tell you stories and do the usual handwaving dance to convince you (if you appear in-the-know enough to be worthy their reply) why their unprovable assumptions were "natural" and why the "loophole" isn't likely to change their conclusions, should it ever be possible to do experiment without it. Yeah, sure.
And that is the bottom line. Just like with my "assumption" about your location 1 minute ago, I could dance and handwave all I want, why it is "natural" to assume, provided there are no witnesses to contradict me (i.e. data missing for good), that you were 1000 miles away, unless one can show without such assumption existence of the 1000 miles a minute vehicle, why should anyone believe it. Or fund it with their tax dollars.
When you peel off the layers of technical jargon and euphemisms (such as "loophole") protecting the dirty little secret and its priesthood's well being from the outsiders, that's the vital presumed "fact" on which the whole marvelous technology of Quantum Computing rests on -- the wishful assumption about the unmeasured, unmeasurable and irretrievably lost data points.
"If one existed, a quantum computer would be extremely powerful; building one, however, is extremely challenging,"
Extremely challenging, like in "it can't work and it won't ever work, but I hope the government and the industry sponsors won't find that out, at least until I retire, preferably after I am dead."
The whole field of Quantum Computing is a mathematical abstraction (fine, as any pure math is, as long as you don't try to claim that's how the real world works). Its vital connection with the real world is based on a highly dubious (even outright absurd, according to some physicists, including Einstein) conjecture about entangled quantum states (roughly, a special kind of "mystical" non-local correlation among events) which was actually never confirmed experimentally. And without that quantum entanglement the whole field is an excercise in pure abstract math with no bearing on reality.
While there were number of claims of an "almost" confirmation of this kind of quantum correlations (the so-called Bell inequality tests), there is always a disclaimer (explicit or, in recent years, between the lines as the swindle got harder to sell), such as "provided the combined setup and detection efficiency in this situation can be made above 82%" (even though it is typically well below 1% overall in the actual experiment; the most famous of its kind, Aspect experiment from early 1980s had only 0.2% combined efficiency, while 82% is needed for actual, "loophole free" proof) or provided we assume that the undetected events follow such and such statistics, etc. The alternative explanations of those experiments (requiring no belief in mystical instant action-at-a-distance), which naturally violate those wishfull assumptions, are ignored, or ridiculed as unimportant loopholes when forced to debate the opposition, by the "mystical" faction. After all, without believing their conjecture all the magic of quantum computing, quantum cryptography, quantum teleportation, along with funding, would vanish.
For those interested in the other side of these kinds of claims, why it doesn't work and why it will never work, check the site by a reputable British physicist Trevor Marshall, who has been fighting, along with a small group of allies, the "quantum magic" school for years:
Unfortunately, the vast bulk of the research funding in this area goes to the mystical faction. As long as there are fools with money, there will always be swindlers who will part the two.
For a more popular account, accessible to non-physicists, of the opposing view, you can check a site by a practical statistician (and general sceptic) Caroline Thompson:
... it's time to get serious and do something that actually matters.
Like what? Write your congress-person? Vote for Al "The father of Internet" Gore (he is these days for "privacy," right)? Or go whine on messsage boards dedicated to "stuff that matters."
Do you have something you feel like you should be hiding? If you've done nothing wrong, what's wrong with telling the truth?
Maybe you should go live in a glass house, so anyone passing by can see you and your family, any time, anywhere and anything you do inside. If you're not doing anything "wrong" what is there to be ashamed of? After all, you could be hiding drugs in your tubby-time ducky, or you might be, while sitting on your potty, shuffling photos of nude underage girls in your left hand. If you have got nothing hide, why shouldn't all the good citizens and the good authorities be able to see you while you're in a tubby or on a potty?
(I guess, they must have stopped teaching word "privicy" in these enriched skoolz. Or maybe it is a dirty word now.)
While AOL 6.0 users can still connect directly from the browser to different Internet sites,
Really, we can connect directly to Internet sites? Whoa! And different ones, too. Whooa squared. Thanks AOL, that's something. I knew it, if anyone could pull it off, it would be the genius of AOL.
doing so requires a more cumbersome process than in previous versions of the software.
I guess that must be the bad news part. Oh, well, nothing is perfect. "Cumbersome" is relative, anyway.
I would let them merge with TW-CNN, all the sooner they will both self-destruct. After all, looking at the Bell curve, there are only so many higher primates to the left of the moron line. (I guess CNET somehow managed to find one to write that story.)
Re:/. edit box (Was: See what happens when you...)
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However, HTML forms are rather limited which makes the interface designer's job difficult: What about those with 640x480 resolutions for example?
One can customize here anything one can think of, and then some, when dealing with displaying the threads. That component is one of the better thought out than any I've seen. It doesn't seem beyond the current technology to have an extra checkbox on the customization screen to select small or large edit box. And if the author of this component really gets creative, some day we even may get the medium size option, too.
Re:/. edit box (Was: See what happens when you...)
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Are you saying to reply, one should switch to desktop, launch an editor, keep switching back & forth as needed to reply in the context, then when all is done, issue 'select all' command in the editor, then do the cut, then switch to the browser, then paste from the clipboard into the browser, then switch back to the editor, then click close on the editor window, then reply to the editor dialog box that you are sure you don't wish to save anything. And then multiply everything many thousands times for all the posters here. Just so we could spare the poor web designer the trouble of having to try out her creations, so she can concentrate on 'stuff that really matters', say, her H1B forms.
Now there is an elegant solution. Who would have ever thunk of that. Well, it is true, human is an adaptible animal, he can get used to anything if he applies himself.
Re:See what happens when you rely on NT
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They instead have to totally re-think how Outlook (and other Internet software) handle untrusted
binaries (that probably includes ActiveX).
It could have been in the attached MS Word.DOC file as well. And anyone who goes to ther MSDN site for various tech info, having to use IE with full ActiveX enabled to make the sites work right, is potentially infected. Or anyone using the MSDN Libraries, including MSVC Help, of recent couple years (which also don't work well without internet connection enabled).
Their whole "vision thing" of hypertext documents which seamlessly integrate your computer (via the MSDN Libraries, including compiler help files) into the Microsoft servers, reporting (if they wish so) anything you look up, any articles you read and for how long, anything you search for, which code samples you extract,... even without coupling with ActiveX, is a virus/trojan handcrafted for industrial espionage, all by itself.
I wish only Bill Gates' machines and those of the other brains behind the Microsoft all-is-one (or is it one-is-all) "vision" got some of their own medicine.
BTW, I just typed in my first message in here, and this luxuriously spacious/. edit box with its eye pleasing courier font makes Microsoft Notepad seem like an ultra-ergonomic editor from the future. (The only cure for this is to make the web designer here use this exact edit box for three days for all of her editing work; by the second day the edit box would be twice as wide and three times as tall and user could set their own non-fixed pitch fonts. By the third day she would suggest dumping it altogether and using something like Userland's Manila editor.)
.to quote Einstein apropos Quantum Theory:
"God doesn't play dice with the Universe".
Now we know that not only does God play, he uses loaded dice !!
Although Einstein's view on QM is today a minority view, it was by no means disproven, experimentally or theoretically. While there were numerous claims of "disproof" of both kinds, it is now recognized that the theoretical claims (based mostly on von Neumann ideas from 1930s and Kohen-Spceker theorem of 1950s) are invalid. The experimental claims of "disproof" (based on tests of Bell inequalities from 1960s), while considered by the majority as very suggestive, all have fatal "loopholes" (euphemisms for "it almost worked").
Since there is no experimental or theoretical fact which would distingush between the two interpretations, there is no basis in claiming that great scientific successes of 20th century are based on the (present) majority interpretation (core of which is: intrinsic randmness, no local hidden variables, quantum state collapse or projection postulate). Nothing as yet follows from it which has any tangible/measurable consequences i.e. among others there is no quantum computing, quantum cryptography, quantum teleportation,... these are all wishful pipe-dreams (useful only in attracting funding from the ignorant and peddling quantum mysteries paperbacks).
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I agree, Bohm theory isn't the real thing. As Einstein said, it was too cheap. Its main virtue was that it had served as a direct counterexample to the von Neumann no-go theorem for any hidden variables.
The origin of its inadequacy and the main source of its difficulties was in retaining the QM's 3N dimensional phase space for the N particles. That made it easier to map into the QM, to show the equivalence of their predictions, but at the cost of turning the theory into conceptual dead-end.
There are several much better alternatives, in particular the nonlinear field theories of A.O. Barut and E.T. Jaynes. They went back to the Schrodingers original idea when he came up with his equation: he intended to take the classical Maxwell equations coupling charged particles and the EM fields, then replace the Newtonian point particle currents with his Psi field (the wave function) currents. Unfortunately, the resulting system is a set of nonlinear partial differential equation, which were far beyond the mathematical techniques of his day. Additionally, an unfortunate computational error he made in one of his initial tries with this approach (on a simpler example), convinced him incorrectly that it wouldn't work even if he could carry the fuller calculations out. So he gave up on it.
It was only in early 1970s that Jaynes noticed the error and carried out more complicated calculations, finding that it actually works. He then expanded the idea into, what he called "neoclassical theory" which was supposed to be a conceptually clean alternative to quantum electrodynamics. But then, as with Schrodinger, a computational mistake in attempts to replicate QED predictions (after severa successful examples) sidelined the "neoclassical theory."
In mid 1980s, A. O. Barut found and fixed that error, and developed it into "self-field theory" with an impressive volume of work (helped along by several younger collaborators) and replicated many QED results, including the higher order radiative corrections, as far as they could compute them and beyond any experimental accuracy at the time. Thus they did demonstrate that as far as the agreement with the major experiments, QED had no advantages over the self-fields.
Conceptually, of course, the self-fields were far cleaner theory -- just the coupled interacting (and self-interacting) classical matter fields and EM fields, with no orthodox QM absurdities or QED divergencies. In principle the model was capable producing the mass of electron (or the fine structure constant) from the first principles, and they did manage to get some relatively crude soliton-like solutions and electron mass approximations (the nonlinear partial differential equations involved were very difficult, even by todays standards).
Barut's group also failed to demonstrate the equivalence of the self-fields to the predictions of QED to all perturbative orders. Then A. O. Barut died in early 1990s, and the group lost its track, each of the younger guys went their own way.
There are still some Russian and Ukrainian physicsts pecking at the variations of the Barut's self-fields (such as Oleinik, who claims to have obtained good approximation for electron mass from it), but it hasn't overall moved very much since the Barut's death. Jaynes, who inspired by Barut's results, went back to rework his "neoclassical theory," also died recently, so that work is left orphanned, too.
Another class of theories was spawned from the Nelson's stochastic formulation of QM from 1960s, which from stochastic mechanics grew into electrodynamics, named Stochastic Electrodynamics (SED). Marshall and Santos group has in recent years developed furhter a subfield of SED dealing exclusively with quantum optics problems, they call their model Stochastic Optics [SO]. The SO has reproduced the experimental results of all the major PDC based experiments of recent years for testing Bell inequalities or demonstrating other "non-classical" properties of photons.
The SED/SO use classical EM theory supplanted by the random background EM field (Zero Point Field) and classical point particles for the charged particles (or, in some variants, the Schrodinger eqation, with the external EM field approximation, i.e. without the self-interaction). Although more effective in producing the final results than Barut's self-fields, the two theories can be seen as one fundamental theory (the self-fields) and its computationally more practical (external EM field type) approximation, the SED, where SED simulates the complicated self-fields via the stochastic EM background and the soliton solutions of the self-field with point particles in this stochastic EM field. In the last couple years, Marshall has moved toward expanding SED toward extended particles and their stochastic fields, while retaining the stochastic EM background. Whether that will improve SED so that it can replicate more of QED predictions (beyond the quantum optics, where SO works quite well), it is not clear at present.
There have been several other more exotic variations among the alternatives to QM/QED in recent couple decades, but I think we are reaching the practical limits of the slashdot's message board scheme, so I'll leave it for some other occasion. Thanks for the nice discussion. You can have the last word in this thread, if you wish.
That is a correct -- the inequality doesn't exclude any LHV theory a priori. But when the experimental results are being adjusted, to match the so-called "ideal QM prediction" ("ideal" is an euphemism meaning that it doesn't actually predict the data correctly), the additional assumptions, claimed by their advocates to be "reasonable," are introduced which all by themselves exclude the whole classes of HLV theories (for not complying with these "resonable" additional requirements). So that is how the "resonable" HLV constraint comes into the play here.
It is a question open to experiment whether nature violates Bell's inequalities. We seem unable to agree on whether Bell violations have been measured.
It is not a question at all, for anyone with some knowledge of the subject, whether any actual experimental data so far had violated Bell inequalites. None ever did. Not a single experiment had such data.
What violated the inequalities in all experiments making such claims are the adjusted data, the data filtered out and modified based on some arbitrary and unprovable assumptions. Consequently what the experiments exclude is not an arbitrary LHV theory, but only a subset of LHV theories which, not only reproduces the measured results (and some do so quite well), but also complies with those ad hoc assumptions (which come from no basic postulate or experimental results; after all, they are put in by hand precisely because they don't follow from anything else).
If they have been then locally real theories are wrong (not that quantum mechanics is right). If they weren't violated when they should have been, then quantum mechanics is wrong. There aren't any other choices.
The sticky part is "when they should have been." Namely, if you have a theory which supposedly corresponds to reality (as far as experiments can establish), say QM, then the results of Bell inequality tests should match this QM prediction. They don't. But that doesn't mean QM is wrong.
Specifically, the Bell's QM "predicition" showing that QM ought to violate his inequality is very sketchy, back of the envelope style, which ignores many additional effects in any real experiments. So it is no wonder that such "prediction" doesn't match the data. It is not a real prediction but a sketch, a hint for someone to do the full calculation, taking into account all the effects involved in a real phenomenon (i.e. it should be a full Quantum Electrodynamics [QED] calculation, not the little skeletal calculation of the Bell's paper).
If anyone had ever made the full QED calculation of any Bell inequality experiments, the prediction of such full calculation would match the obtained data, no one on either side doubts that. (The non-relativistic QM is not suitable for such prediction, except as a rough indicator of qualitative behaviours.)
In other words, the full and exact quantum electrodynamics prediction, capable of predicting the actual data (the average photo-detector counts obtained), does not violate Bell inequalities in any of the set-ups tried so far.
The only thing which has ever violated the inequalities is the "ideal QM prediction" which is the prediction Bell sketched in his papers (deduced using orthodox QM collapse interpretation), and which doesn't match any actual experimental data.
And, obviously, any synthetic "data" (the data obtained from the actual data via ad hoc adjustments and filtering to match the "ideal QM prediction") will violate the inequality.
Therefore there is not a single known experimental setup to date for which the full quantum theory (QED) prediction would violate the Bell inequalities. Namely, if there were such set-up, since the full QED prediction would predict the actual data correctly (it would have computed detector efficiency and noise levels), we would have had already a loophole free test.
It is unfortunate how the ideological zealotry in this field, the desire to uphold the orthodox QM interpretation with its collapse at all costs, has distorted the normal scientifc procedure. Normally, when you get data that don't match the theoretical prediciton based on the initial model (the Bell's sketchy QM calculation), one would try to refine the model, include additional effects which may have been overlooked in the initial model, and see if that agrees with the experiment better. Additionally, an experimental setup would be modified to control better any unforseen and undesired effects.
But in this unique case, contrary to all common scientific practice, instead of refining the model, the data already obtained gets subjected to additional substantial alterations, rationalized by ad hoc, unfounded and unverifiable, conjectures, to bring them into agreement with the sketchy, incomplete model (the so-called "ideal QM prediction" as sketched by Bell). And all that trouble only to avoid disturbing, or even casting doubts on, the orthodox version of collapse used in the essential way to obtain that so-called "QM prediction."
If somehow the Bell inequality tests are not so charged with emotions and high stakes, if they were just some result in an obscure paper that nobody cared much about, and that a professor had assigned to a graduate student to test experimentally, and if the student, having obtained the results and having noticed they don't match the predictions of initial crude model, had decided to keep the model anyway (figuring it is too much trouble to work out a more realistic one), and instead chose to modify the obtained data to fit the crude model, rationalizing that he is only making "reasonable" (at least to his and his family's personal satisfaction) assumptions and adjustements --- well, that student would likely get thrown out of the school for research fraud (these things have happened).
Alternatively, say you took a group of physics students, educated them for several year in such a way that they never had any access to Bell inequality, hidden variables or the related controversies. At the end you give them the setup used in Bell inequality tests and ask them to obtain results of coincidences and come up with QM/QED model describing the situation. Not in a million years would any of them just come up with the kind of convoluted reasoning and rationalizations to tweak the data you see in the actual papers on these tests. They would obtain the same data everyone else obtains (but they wouldn't know it would be desirable if the data could violate the Bell's inequality), they would work out the QED model which, if you had picked the batch of the brightest, would match to a reasonable degree the data obtained. And neither data nor the QM/QED prediction would violate inequalities, and they would be perfectly happy.
It takes years of conditioning into the particular absurd twists and turns and leaps of logic at the just right places of these kind of experiments and their analysis, to ease someone into "cheating" on the Bell tests and not feeling any guilt or even being aware they're doing it. All the dubious leaps, which would normally raise red flags in a mind of any rational person, have been drilled into the fully automated operation, into habits devoid of any thought or doubt.
It is true that the predictions of quantum mechanics violate Bell's inequality (that's why Bell's inequality is interesting).
Well, as explained above, that is not true. A real quantitive QM prediction, the kind you can compare its figures with the experimental data and obtain a good match, requires a massive calculation specific to a given experimental setup (including the full initial and boundary conditions, to solve the partial differential equations and inclusion of effects of all dynamical laws involved). And if the QM is correct and the model of the experimental setup is properly constructed, the QM prediction ought to match the data obtained. And since data obtained in any set-up to date had never violated the Bell inequalities, not even remotely, that means that the so-called "QM prediction" which violates the inequalities, isn't a real prediction at all, but a glorified thought experiment supplanted by a bit of "back of the envelope" sketch of QM-like calculation, useful at best for qualitative or heuristic purposes, but of no much use for the quantitative predictions of this phenomenon.
You are objecting to the part one of my message. The connection you are talking about is the essence of the part two of my response. In brief:
- a) If the empirical tests cannot show (loophole free) the violation of Bell inequalities, that implies there is no justification or need for the orthodox version of collapse and the rest of its "measurement theory." The collapse, to the degree it occurs, would then be a consequence of some underlying (local, nonlinear) dynamics, like some type of phase transition.
Thus the empirical (loophole free) confirmation of the Bell inequality violation is the only thing which would uphold (and not very convincingly, at that) the orthodox version of the collapse.b) If the empirical tests do show (loophole free) the violation of Bell inequalities, then any underlying local dynamics (local realism) is excluded. That still doesn't mean the orthodox interpreation or its version of collapse is valid, it merely prolongs its viability since no good alternative is available.
The Bell's theorem as a theoretical reuslt is what had placed the same question [i.e. is there any need for orthodox "mesurement theory" at all (including its state collapse)] in a testable form, giving thus the orthodox interpretation the lease on life pending the definite experimental results. Following the fall of von Neumann's and Kochen-Specker theorems (as proofs of impossibility of any hidden variables consistent with QM predictions), the orthodox interpretation had no reason to exist, no reason for its version of wave function collapse, since everything could, at least in principle, understood as a result of some, presently unknown, underlying dynamics.
The above shows how the Bell's inequalities and their empirical tests (if case (b) occurs) support the orthodox interpretation and its version of collapse.
The other side of this coin is that the theoretical Bell's inequalities rely on the orthodox interpretation of collapse to deduce its QM predicion (which sets LHV boundary in the inequality). So the boundary in the inequalities depends on the Orthodox form of collapse.
Now, it turns out the experimental data don't violate the inequality. Normal scientific method would in that case be to work out a more accurate QM model (to replace the QM side of Bell's inequality) which can replicate the actual data as it was measured. After all, the detector's efficiency (or the background "noise") isn't some god given untouchable and unspeakable decree, but it is one of the physical/QM properties of the experimenal system.
Instead, the orthodox school had merely renamed the Bell's QM prediction as "ideal QM prediction" and then gone out their way to fix the "non-ideal" experimental data, based on several unverifiable ad hoc assumptions, which are outside of the postulates and which almost by definition exclude LHVs all by themselves (with no tests needed, e.g. the "fair sampling" is directly contradictory to what one would expect from almost any LHV - that the particle detection does depend on LHVs [what else could it depend on but HVs, anyway] - the "fair sampling" imposes upfront the condition which excludes any LHV theory with such dependence.)
You seem unconvinced that they have been measured, and I can respect this position to the extent that there are genuine flaws in the experiments.
What I am saying about the tests is not a matter of convictions or tastes at all. What the test have excluded is not all LHVs but the LHVs which satisfy not only the normal requirement to be able to replicate the experimental data (or equivalently, to replicate the exact, not just "ideal," QM predicitons, which of course ought to agree with the actual data, as well) the additional assumptions applied to the experimental data to bring them into agreement with the "ideal QM predictions" of Bell's inequalities.
The only thing which is a matter of tastes or convictions is whether these additional assumptions are "plausible" or "reasonable" constraints on LHVs. But there is no dispute at all whether these additional assumpitions are being made -- anyone with any knowledge in the subject knows they are being made.
Now, to see whether these additional constraints on LHV are actually plausible and reasonable, one has too look at a variety of proposed LHVs which can replicate the experimental data of those tests and check whether they satisfy these additional constraints.
If you check the literature (especially those from the Trevor Marshall, Emilio Santos and their school) you will see that those additional, innocently sounding, contraints are preposterous -- they exclude reasonable theories (such as Sotochastic Electrodynamics [SED] and Stochastic Optics [SO]) upfront, with no experiment needed. The SED/SO does in fact replicate the data from all the PDC photon experiments for Bell inequalities and for the other so called non-classical effects in quantum optics. To exclude such broad types of theories upfront based solely on what someone wishfully labels "fair sampling" or "non-enhancement" hypothesis, is absurd. At the very least such theories demonstrate plainly that those euphemistically labeled assumptions are throwing out, all by themselves (with no experiment needed to support them) much more than what is usually claimed to be excluded a priori (i.e. by the added assumptions alone).
The two are inseparably entangled, as it were. If one falls the other goes, too.
First, it is precisely the subsystem state collapse, as prescribed by the orthodox interpretation, how the Bell's (or EPR-Bohm) theorem deduces the quantum prediction side of the Bell's inequality. (And this is the same collapse that quantum "computers" are supposed to use to extract their "computation" results out of the entangled states; which is what brought us here.)
Second, as explained in the previous message, the Bell tests were the culmination of a long debate whether the hidden variables are excluded by QM (or its predictions). First there was von Nemann's proof (from 1928), which claimed to prove HVs are inconsistent with QM predictions. That was accepted by the mainstream as the final word, which in turn gave rise to the present form of the measurement problem -- if HVs are impossible, then the statistical nature of QM cannot be due to unknown or uncontrolled values of some hidden variables, being merely revealed by a measurement.
The linearity of the evolution equations of QM precluded the combined system, the "measured system" + the "measuring aparatus" from ever being able to chose or settle into one of possible results. Von Neumann's "solutions" was to declare that it was human mind, the mind of the observer which finally made such decision (this view was also promoted by Wigner).
That was a clear acknowledgment that there is no way the rules of the evolution along with his interpretation of them, especially his no-go theorem on HVs, can reproduce what happens in a measurement -- the system, in real world, does seem to pick somehow one among the alternatives as the measurement result, i.e. it appears as if the state got projected onto the one definite aparatus state (eigenvector).
Others, who didn't like the idea of "human mind" becoming a part of a physical theory, but who bought into the von Nemann's no-go theorem for HVs, kludged from the two contradictory pieces, what nowdays is called the orthodox interpretation. Since the two ways of evolution contradict each other, we will give each a role but never at the same time. How this is to be decided, which one is in charge and when and where it is supposed to switch the rules, that was never really explained. But too keep the physics students from asking too many questions, they wrapped the kludge into the term "measurement" and wrapped all that into the generous layers of warm and fuzzy talk about "irreversibility" "macroscopic aparatus" etc.
Not everyone bought it, of course. One who didn't buy either, the von Nemann theorem or the "measurement" fog, David Bohm went out and constructed an explicit HV theory reproducing the QM prediciton -- in effect showing that von Neumann theorem was wrong.
Well, that meant there was no need any more for all the "measurement" fairy tales, for the two sets of rules and a divine intervention (or a mind), to switch between them. The orthodox school didn't give in though -- all those multitudes of leared tomes and deep papers they produced to "splain" it all, to the simple-minded physics students, who stubbornly clung to their common sense -- all that work down the tubes. No way. All those deep thoughts on complementarity and marvelous connections with the hindu worldview, to dump it all. We can't let that happen.
In the scramble that followed Bohm's theory, the orthodox school kludged quckly another proof, Kochen-Specker theorem. It backed off a bit from the von Nemann's grand claim that no hidden variables of any kind are possible, to a lesser claim that "no non-contextual hidden variables are possible." And since the non-contextual kind was declared good and the contextual kind was declared to be a no-no, everything seemed to be now back where it was before Bohm. The Bohm's HVs were "contextual" hence no good, hence ignore them, shut the Bohm up. Bohm squeeled for a while, but what could he do, everyone's got to eat at the end.
No major objections to Kochen-Specker were allowed into the open for several years, the wavering orthodox line was held, until John Bell published his paper showing (what Bohm and everyone else who cared about the whole mess, already knew) that the Kochen Specker theorem suffered essentially the same flaw as von Neumann's, so it is no good. But since Bell had another proof in his paper, the Kochen Specker fell, the Bell inequalites arrived. They did retrench a bit from Kochen-Specker, but better something than nothing, since Kochen-Specker could not have been held for much longer, anyway.
The core claim of Bell inequalities is that if QM predictions are correct any hidden variables which reproduce these predictions must be non-local. And since non-local is "bad," then no "good" hidden variable theory can exist. And thus the whole mass of learned production from the best and sharpest minds of the orthodox school on the mysteries of the quantum "measurement" is still a valuable contribution to science and a required reading for the poor and stubborn physics students.
So the Bell's inequalities are the last defense line upholding the whole orthodox interpetation -- they provide a need for its existence. Namely, if a local hidden variable theory could reproduce the QM predictions (which Bell's theorem prohibits), then as with the fall of von Neumann's therem, there would be no need for the measurement theory mistique, collapse and the rest. Everything would revert back to common sense, measurement simply reveals the values some variables had at the time of measurement. No need to write "learned" tracts on reconciling and understanding the contradictory or for invoking hindu deities to arbitrate between the two contradictory set of rules.
At the same time, as pointed out at the top, Bell's theorem uses, none other, but orthodox interpretation of collapse to deduce what the QM prediction ought to be. So, it is a mutually supporting arrangement, between the Bell's theorem and the measurement theory of the orthodox interpretation -- if one falls, the other has to go. Well, one must admit it was cleverly crafted. But the nature (un)fortunately is the last judge what ought to happen. The actual data from the experiments showed no violation of Bell's inequalities. What to do now?
Well, the clever folks who fought off valiantly the great Einstein himself, then the scary Bohm's assualt, surely won't fold their wares just for some little experimental data. So the Quantum side of the Bell's inequality (the supposed QM prediction based on the orthodox interpretation of subsystem collapse, which violates inequality, but doesn't match the actual measured data) was relabeled "ideal QM prediction" and the experimental data, by implication, as non-ideal, thus in need of fixin', requiring the massive hand adjustments of the obtained data points, rationalized by a variety of unverifiable assumptions pulled with a lots of handwaving out of a magicians hat ("massive" as in changing or injecting 990+ points on of every 1000 presented as the final all nice and fixed-up result).
Ain't that so convenient. Instead of, as anyone with an ounce of common sense would suggest, producing the correct QM prediction and comparing that to the experimental data, the alleged QM prediction of the Bell inequality is kept as is (since otherwise, of course, there would be no inequality for the correct prediction, the one that matches the actual data -- hence no Bell theorem, hence the last defense line of the orthodox dogma would fall) and the experimental data is wishfully twisted around to bring it into compliance with this alleged QM prediction.
Unfortunately, a poor physics student taking courses in QM has no chance of disentangling this ball of tangled up nonsense which has come to resemble talmudic law or some such endless web of legalistic word games.
The new line of defense (to become effective as soon as a confusing enough theorem can be put together), is going to be "decoherence" (an euphemism for incoherence, I guess). That is when the "quantum entanglement" (another very appropriate name) will be quietly dropped.
NOTE: I am not suggesting above that someone actually set down and plotted out all the twists and turns of the developments described. No need for that. It is the phenomenon of the same kind as the Adam Smith's "invisible hand" guiding the economic developments as if they were cleverly planned, even though there is no explicit plan and every player is merely pursuing their own narrow self-interest. Science does operate as a marketplace of ideas and models.
Well, that's a different topic. All they did is create an entangled state (which is the type of state serving as an input into the Bell inequality tests). Even the classical Maxwell equations allow for entangled EM wave packets of the same form. From theoretical viewpoint they're just one form of initial & boundary conditions, there is no controversy about it at all. The classical entangled EM wave packets do not violate Bell inequality. (And neither do the quantum ones, as far as anyone could measure to date.)
A computer built on such 'classical entanglement' would be merely an analog computer, having no special powers. And neither would QC, unless one can establish the additional very special properties of that state, the subsystem collapse which the Bell inequality experiments were devised to test.
The paper doesn't even try to prove that those states exhibit the subsystem state collapse property, which is the point of Bell inequality tests. It only deals with preparing particular initial & boundary conditions, which is fine (and probably useful), but not relevant for the subsystem collapse hypothesis or the Bell tests of it (which in turn is the only way the QC could read off the results of the "computation").
The common interpretation of Bell inequlity tests is merely another manifestation of the problems which were part of QM since the projection postulate (or wave function collapse) was introduced in 1920s. The EPR phenomenon was application of the projection postulate to the subsystem, in order to show how absurt it is. Bell's inequality came in 1960s (and tests in 1970s), when QM was already four decades old.
Einstein and Schrodinger who were among the handful key founders of QM did not accept the wave function collapse from the start. It was absurd, an ugly kludge trying to hastily patch up the holes in, what at at the time was, immature new theory, to make it appear complete.
The core absurdity of the projection postulate is that it switches the rules of how the system evolves midstream -- suspends them at an undefined moment in time, based on no objective criteria, for undefined length of time, then changes the state of the system in a way cotradicting the original equations (which were "luckily" now suspended, otherwise there is a contradiction), then the new rules suddenly go away, at some undefined time and for no rime and reason, and the old rules are said to hold again.
It is one ugly kludge devised to patch up the contradiction between dynamical equations and the presumed effect of measurement -- since you can't have two contradictory rules in a theory, the "solution" was to effectively inject divine will into the game and have it willfully switch the rules midstream back and forth, as it pleases.
The Bell's inequalities were devised (by late John Bell) to serve an experimental test which would decide whether this switching of the rules is really necessary -- whether there may exist a single set of "reasonable" rules (i.e. without instant action at a distance), which always hold, which need no divine intervention to suspend them and then let them work.
The way I see the experimental results so far is that indeed the test does show that the existence of a single set of rules is consistent with the experimental data. Only when the proponents of the divine intervention (the collapse kludge), sticking with that style, I guess, inject yet more divine intervention, the arbitrary hand-put assumptions (which are outside of the postulates of QM agreed upon upfront), which conveniently let them weed out (or inject new ones) the data points after they have them already at hand -- only then these hand-tweaked "improved" data excludes the possibility of the single set of rules. Well, who would have guessed that.
So, ignoring the euphemisms and other verbal gimmickry (e.g. talking about "loophole free proof" instead of "proof that actually works" or "proof that proves" or just "proof") and silly little games with data after the "bad news" are in -- the nature, as far as it has revealed itself until now, seems to be perfectly happy in using single set of reasonable rules. The rules we don't know as yet, but which are not excluded by any facts known to date.
The ion based tests open their own set of loopholes, while closing the common photon tests loopholes.
Unlike photons, ions can be detected with high efficiency (theoretically 100% since they're massive particles). But since the spin coupling energy (with Stern-Gerlach magnets, the analogue of polarizers in optical experiments) is much lower than their kinteic energy, the spin measurements (selection) are much less reliable than those of optical photon polarizers. This results in large background counts (due to depolarization) and this subtraction is a well known loophole for LHV models (also occuring with photon tests when the sensitivity of the detectors is increased).
Additional problem is in reliable production of the entangled pair state, again due to the low energy of spin-spin coupling (between the spins of the ion pair) relative to other energies involved in the process of pair production and collimation. The result is again a large number of "accidental coincidence" detections, i.e. another contribution to the background to be subtracted.
Hence the background subtractions make ionic tests very similar to the case of photon tests when the photo-detection is increased to near 100%. This can be achieved by using very high energy photons (e.g. gamma photons from the electron-positron annihilation), in which case one can have near perfect detection, but polarization measurement doesn't work too well (via Compton scattering), producing very large background which needs to be subtracted (exactly as with ions, and for essentially the same reason).
An alternative way to increase the photo-detection efficiency is to use very sensitive (low threshold) detector, but that produces large dark current, the background noise, which again has to be subtracted. The resulting unsubtracted data in such case are almost exactly what a classically entangled EM wave packet would produce (i.e. what Maxwell equations would predict). You can, for example, see the actual raw data from Asepect's PhD thesis, where he did his famous cascade experiments, on Caroline Thompson's web site. For more modern PDC based experiments, see the similar Stochastic Electrodynamics models (which are again the Maxwell equations based models, but with stochastic initial & boundary conditions) which reproduce the raw data for these experiments, on the Trevor Marshall's site.
It is true, as far as I know, that no single experiment has gotten sufficient sensitivity using spacelike separated measurements... yet. It seems somehow perverse though to hang a defense of local realism on this fact.
This is the oldest handwaving argument for dismissing the loopholes in Bell tests, i.e. why would some future increased sensitivity (for detection or polarizer efficiency) suddenly switch from the good agreement with QM (modulo loopholes) and give preference to the local realism.
First one should note that the non-adjusted experimental data is already consistent with the local realism (and there are numerous local models for variety of the setups reproducingt he experimental non-adjusted data). So nothing here has to change for more sensitive experiments. Only the wishfully adjusted data (when the loopholes are dismissed via ad hoc unverifiable assumptions) exclude local realism.
Second, it is perfectly natural for any local realistic model to make the efficiency of the detector or polarizer dependent on the values of the local (hidden) variables. Such dependency is outright excluded by the fair sampling (be it sampling by the detectors or the polarizers; in the ion case the critical fair sampling problem is at the Stern Gerlach magnets, the "polarizer," not the detector, which is here near-perfectly efficient; while in photon case it is at the photo-detectors, and not at the near-perfect polarizers). The ion tests only shift the fair sampling (in the hidden variable space) problem closer to the source, at the Stern-Gerlach and the pair source production depolarizations (which results in the background counts, which is presumed to be a fair sample in the LHV space, thus it is flatly subtracted subtracted from the total counts).
To illustrate this point in a form more accessible to non-physicists here, consider a national poll using email. Such poll will fail to detect people who do not have computers with internet connection and email account. Suppose now the poll analysis expert wasn't informed about the method of communication used to obtain the poll data. This is analogous to the Bell test experimenter looking at the counts of particles detected, but not being able to measure or know anything about the so-called local hidden variables (analog to the email, which is here invisible variable/value to the poll analyst).
The analyst, not knowing anything about the underlying means of communication, proclaims now that he will assume that the chance of being detected by the pollster doesn't depend on the (invisible to him) method of communication, hence the sampling is proclaimed to be fair, by declaring it to be so. This is exactly how the experimenters in the Bell tests establish that their sampling is fair (at detectors or polarizers), independent of the hidden variables -- by proclaiming it to be so.
Now suppose in our poll, a question asked "what was your income?" Clearly, the sample is biased here, and the income discovered this way will be higher than the national average. In other words, the poll is more sensitive in "detecting" higher income than lower income people. In the extreme, if the question is "are you homeless," the sample will completely miss any homeless person, i.e. this "detector" is made completely insensitive to the "homelessness" by virtue of the particluar value of the hidden variable (the means of communication = email). OTOH, if the means of communication were walking through the parks at 10PM, and asking anyone encountered the same questions, the results would be biased the other way. Here the hidden variable "means of communication" = "asking people in the parks at 10PM" -- the variable has different value, and the detection profile is quite different.
In other words, the hidden variables will perfectly naturally bias the sample, almost by necessity, since they do affect (or are correlated with) what is detected and what is missed. Ruling out the sample bias by fiat (as is done in every Bell test), is effectively excluding the hidden variables upfront, by declaring it so.
The issue with QC is that it is advertising itself as a physical theory, and even being promoted as an applied physics or enineering based on a dubious and unverified link with the reality.
Of course, there is nothing wrong in scientific conjectures, as long as they're being labeled as such, with clear and honestly acknowledged distinctions between the facts and the hypotheses.
In case of QC, the weak hypothesis at the root of that theory is labeled as a fact (the subsystem state collapse, necessary to read off the results of the "computation").
Even worse, the legitimate critics, including some reputable physicsts with many years of publishing well received and cited works, end up getting gagged by the peer review "priesthood" (as Trevor Marshall, one of such critics, calls them), their research grants somehow dry out, as soon as they point out that emperor has no clothes, that there is a rot in the core this hyped-up discipline.
Sure, and I got a nice bridge I could sell you, real cheap.
The detector efficiency alone on the photon wavelenghts normally used won't get you beyond 60%, if you wish to take huge noise, 30% and up depending on wavelengths (which in turn requires background subtractions, invalidating the experiment as a "loophole free" Bell inequality test, ie. it fails to exclude the local hidden parameters).
But if you reduce the detector trigger thresholds (such as using ultra-low noise low temperature photo-multipliers), to reduce the noise down to 1-2 percent, the sensitivity, hence the detection efficiency, drops down to 20% or below. It is a no win tradeoff, you either get noise or you get low sensitivity, invalidating in both cases the "loophole free" status for the experiment.
The parametric down conversion (PDC) sources used nowdays also give outright 50% loss, making them entirely unsuitable for the loophole free test. Of course, if you accept additional hand-put assumptions (which are unverifiable and which are outside of the QM postulates), you can handwave it as unimportant.
One try to improve detection efficiency, without noise, by going to higher frequency photons, but that has a downside in decreasing the polarizer effectiveness (depolarization increases). Thus for the ultra-high frequency photons, such gamma photons, which can be detected at near perfect efficiency, the optical polarizers don't work at all, and one has to use Compton effect to obtain very low power effective polarizer (these tests have been done, too, but are of much worse quality than those with the optical photons).
Then you get aperture and geometric losses, which often exceed all other (small aperture is often chosen to avoid noise, reflected photons and accidental coincidences from the multiple sources). Again, these can be adjusted away via yet another hand-put assumption.
To test Bell inequalities in a loophole free experiment, none of these adjustments on the raw data may be done, and the net efficiency on the raw data has to be over 82%.
The grant savvy experimenters have in recent years gotten into habit performing several adjustments implicitly (usually embedded into the software operating the setup) and then quoting as their setup "efficiency" the figures of some minor hand adjustments done at the end (such as polarizer losses), ignoring to mention the extensive data "cleanup" done by the software. That kind of gimmick may be fine for engineering aplication, but has no bearing on the Bell inequality tests.
The only thing which could remotely come close to 99% (if you haven't made the figure up, as it seems likely) would be if someone had "assumed away" all other adjustments, except for the depolarization, which may be brought to 1-2% in losses (for optical photons and if the aperture is made very small; of course, then the aperture losses become quite large, well over 80% losses just from that).
If anyone tells you they have made a "loophole free" Bell inequality test, they're trying to be humorous or are flatly lying. Since nothing is even remotely close to it and anyone even casually informed in the field knows it perfectly well. It would be like someone telling you in confidence to run and buy Intel stock, since they have a new Pentium prototype running at 500 GHz. You would know right off it ain't so. With or without adding the beowulf cluster.
Research and experimentation are rarely a waste of effort, whether to prove or disprove, because we have to find out. The skeptics said we would never build aircraft, split the atom, travel safely in railway carriages, go to the moon, etc etc etc.
The key difference from your analogy is that in your examples, the skeptics were the establishment physics, the folks who decide what is published and what gets funded, while the people claiming something is possible were the outsiders to the establishment.
In the case of QC and quantum entanglement, it is the establishment which claims something is possible while the heretics claim it isn't. So, the much closer analogy is the case of medieval church, an establishment of that era, claiming various superstitions and miracles are possible, while skeptical heretics (such as Galileo or Bruno), who were outside the establishment, claimed that was bunch of bunk.
Any experimenter who did such experiments (and there were dozens of experiments over the last 3 decades) will acknowledge that the experiment was not "loophole free," which is a euphemism for "the actual data didn't confirm it, but if I assume certain statistical properties of the photons that escaped detection (and which, luckily, no one could now show to have been one way or the other), and then remove the data points which don't fit such assumption, and also fill in the gaps for the missing points (which just happen to make up 995 out of 1000 final data points) with the points having the assumed statistics, then the statistics of these new and improved data points does violate Bell inequalities, proving thus the quantum entanglement." That's what it comes down to, when you peel of the jargon, the handwaving and the euphemisms.
Go to the Los Alamos preprint archive (I gave the link earlier), pull the emails of the authors claiming such verifications and ask them whether their experiment was "loophole free" (none was) and when is the "loophole free" version scheduled to start (not scheduled, not designed, not within present detector technology).
Or you can got to the Los Alamos preprint archive and find hundreds more preprints on the same topic.
Preparing desired state, while often technically challenging, is not the weak point of the QC. Reading the results of the "computation" is where the scheme will turn out a dud. See my other comments in this sub-thread on why that is so.
I'm curious what motivates your objection to quantum mechanics. Do you reject the mathematical theory of quantum mechanics (in all of its various guises) which has held up rather well to experimental validation, or is it instead that the heuristic, post-Copenhagen interpretation of the theory (i.e. "spooky action at a distance") rubs you the wrong way?
My objection (and Einstein's, too, among others) is against the branch of QM which grew out of the state collapse postulate (that "fruits" of which include QC and quantum teleportation). That is a postulate independent of the rest of the postulates (the ones that successes of QM rest on), it has no practical or explanatory power.
It is a parasitic useless add-on on which the assorted swindlers have been triving for decades, ranging from the fast-talkers among physicists pulling the fast one on the hi-tech execs and VCs to the the new age gurus on "quantum healing" ripping off little old ladies with bad joints and wide eyed teenagers looking for "self" and its meaning (there ain't one, if you don't mind me spoiling the plot).
The relation of this postulate to the rest of QM is that of a loser exploiting and taking credit for his older brother's good reputation and success.
Caroline is an outsider to the field, but otherwise an intelligent person and specialist in her own field (statitstics), which has great deal of bearing on the interpretation of Bell inequality tests. While I certainly don't buy all of her skepticism, and even less her conjectures about the alternatives, she does have a very sharp eye to spot a swindle, a loophole in setup and the argument. Also, as an outsider, she does present the key issues in a much more accessible way to non-physicists, without skipping over or hiding the tricky points (as popular books by physicsts tend to do).
To separate that postulate from more plausible alternatives (such as "incompleteness of QM," i.e. the existence of additional quantities for which the rest of QM gives only statistical, but individual, predictions), Bell inequalities were devised (by late John Bell), which give a cutoff point on statistical correlations in a special type of multipoint photon/particle detections. If the counts violate the inequality, the "local [hidden, unknown] variables" are exluded as a possible explanation of these experiments. If the counts don't violate the inequality, some underlying [unknown] quantities are consistent with the rest of QM.
It turns out that actual data doesn't come even close to violating the Bell inequalities. Only after great deal of handwaving, aiming to convince that certain conjecture about the statistical properties of the missing data (the instances when the photons failed to trigger detectors) ought to be accepted as plausible, only then they can "adjust" (change to a more desirable form) the data, and lo and behold, the new and imrpoved data miraculously violates the Bell inequalities.
The fact that very specilized experiments are needed to find out whether such subsystem collapse occurs at all (consequently whether QC can ever work, even in principle), ought to tell even non-specialists that the successes of QM have nothing to do with that postulate. It is a parasitic add-on, with no real use (other than parting the cash from the fools who fund the swindle).
See my earlier comment on difference between general entanglement (which is a well established process) and quantum entanglement.
The element necessary in any form of quantum computing, which provides the ability to read out the "computation" result, is the quantum measurement postulate (also referred to as projection postulate or state collapse postulate). For any nontrivial "computation" QC uses its special case, the assumption that a measurement on one subsystem will collapse the state of the remaining subsystem (this is supposed to happen even without any interaction with the remaining subsystem, which could be miles away and physical field/force is needed to carry out this remote collapse).
That element is an independent postulate of the theory. Nothing in actual explanatory power of QM requires it, no great successes of QM (which include much of todays semiconductor technology, where quantum solid state theory, developed in 1950s, helped point the way and provide theoretical tools for the more practical experimental research later) over decades need it. All detector count results are computed using correlation functions (such as Glauber's multipoint correlations used in quantum optics to predict correlations among multiple photodector counts) which don't require any collapse. The collapse is a gratuitous and by itself useless in any explaining (of any observed phenomenon), a parasitic add-on to the theory.
It has no operational use other than in "explaining" the experiments trying to confirm it (and none of them did, unless you're willing to believe several additional quantitative assumptions, about the state of unmeasured and unmeasurable quantities, assumptions which are outside of the postualtes themselves). And of course, they're used in "predicting" the existence of quantum computing, quantum teleportation and other assorted miracles.
Any claim by experimenters to have demonstrated QC, if they're fully honest, will disclaim it the same way Bell inequality tests are disclaimed -- yes it was shown, provided we accept additional assumptions (which are outside of postulates themselves) about the missing (unmeasured and unmeasurable) data. Only the so adjusted "data" exhibit QC or violate Bell inequalites. The raw data (unadjusted detector counts) show no such phenomena. These adjustements are sometimes expressed in terms of extrapolating the results to the sufficiently decoherence free state.
You seem to believe that reality is what you see.
Of course, not. I have been theoretical physicist long enough to know better (and I have been doing lots of other the after the academia to know even better than that). Reality, as far as physics is concerned, is the what the best underlying models say it is, which means it is subject to revision as the models are revised.
What that means is that there is "model," postulates, mathematical formulas and algorithms used to extract the behavior of the models. Model by itself is thus a pure construct. To make it mean anything there is also a set of "correspondence rules," prescribing how the properties of the model map into the observation. This is where the model makes the contact with conventional empirical reality. Without such contact it is not a scientific model, but a pure speculation (the artsy-fartsy stuff).
In modern physics the core components of "reality" of the model (strings, quarks, electrons) are never observable in any direct way. What is actually done is to compute some long chain of (mathematical) consequences of the model, then at the end of chain there is a set of numbers which can be associated, via the corrsespondence rules, with the experimental facts, e.g. with counts in some detectors. If the counts match the numbers produced by the model, and if one can vary the input assumptions of the model while still maintaining this match, well, the model is said to be "reality" behind the phenomenon. Now that doesn't exclude possibility of alternative. The present models of physics don't exclude alternative models. What experiments show is at best that a proposed model is consistent with the experimental facts, not that no other model can account for those facts.
The problem with QC model is that its vital contact with reality (without which the result of the "quantum computation" could not be read off) is that it relies on the state collapse postulate, which so far does not make sufficient difference by itself to be confirmed empirically, in the sense of exluding the common sense alternatives (such as allowing that QM is incomplete, i.e. there are variables missed by the quantum description, which only covers the statistical properties of such variables, but misses their detaled individual properties).
Despite 7 decades of experiments attempting to establish absence of those "hidden variables", including the 3 decades of Bell inequalities tests, no "loophole free" experiment exists as yet. The odd wording, "loophole free" experiment, is a customary euphemism trying to say in a nice way that no actual data in the experiments show what the experimenters wished to show (ultimately, the non-existence of local hidden variables, or specifically, the Bell inequalities violations). Only the fictitious "data," obtained via a very "special" kind of adjustments from the real data does violate the inequalities.
The justification for these adjustments is not the postulates of quantum theory themselves, but are ad hoc one shot assumptions about the unverifiable missing data, belonging to no theory, and useful for nothing else in physics but getting the otherwise "unwilling" data to fit the desired conclusion (violation of inequalities). If you don't accept them (as you don't have to, unless your funding proposal vitally depends on being able to bedazzle the fools with money), no violation follows, no QC (can't read the result of QC, it is still there, allegedly, but it can't be gotten to), no teleportation (and no funding).
Quantum mechanics, yes. But there is nothing ever measured explained by the quantum entanglement hypothesis. It has never even been confirmed experimentally (without loophole), much less that it has any use in explaining any phenomenon actually observed.
That hypothesis is based on an independent (from the rest of QM) postulate on how the composite system state transforms in the measurement. The actual postulate in fact contradicts the normal unfolding of a quantum state (as prescribed by the evolution operators, or Schrodinger equations), saying in effect that when the "quantum measurement" (never really defined with usable precision) is done, the regular dynamical equation somehow cease to be valid, for unspecified time interval, in an undefined way, the state "collapses," then somehow, at some, again undefined, point in time, the normal dynamical equations take over again.
It takes years of conditioning in physics to be able to submit ones common sense to such mind twisting "logic." And even then it never tastes quite right, there is always some fishy odor around it. It takes then more years to be able to snap out of it. But it can be done.
Eventually, of course, the peddlers of quantum magic will have to face the question -- where is the beef, show me the "Quantum Computer." Let's benchmark it. And when the proverbial rubber finally meets the road (which they've been skillfully avoiding for some years; read Kwiat's hedging with "extremely difficult"), the only thing which will collapse will be that whole house of cards.
Anyway, I know a number of folks who are working on various bits of QC research.
The actual Quantum Computing, if understood as a pure mathematical discipline, unrelated to physical reality or actual computing can be quite interesting (to those who enjoy that kind of abstract mind challenge). And it is not impossible that it may end up having some applications in analog computing (the plain classical style) if that can be made to work. Or inspire some neat devices based on quantum dots. One can always stumble into the right thing for the wrong reason. After all, Columbus thought he was going to India, and believed he found it.
These are not shady scientists looking to push alternative theories under the rug and secure government grants on false promises.
Well, that's true of most large scale swindles. Take various large scale superstitions (the religions) -- most priests will sincerely believe dogmas they preach. But try touching the core of the dogma, then you find out how it really works. The peer review in this field, for all major journals and commissions for research grants, is stacked extremely one sided way against anyone pointing to the fundamental flaw of the theory -- the vital experimental connection with reality of the whole QC superstructure is based purely on assumptions about the (iretrievably) missing data. If one makes different assumptions, as one is free to do about something which is unmeasurable, the whole relation of the QC with real world fizzles away.
Now, the old boy network running the peer review in all major physics journals, will let anyone challenge any detail of the superstructure, argue how fast QC will be, will some QC algorithm really work in n*log(n) time or some such. But try touching the vital "loophole," and you might have as well spit at the editors face or kicked the african killer-bee nest -- your manuscripts will be turned down with the lamest of excuses and run-arounds, your grant proposals flatly rejected. Just ask Trevor Marshall, who is quite a competent physicst, and has published many dozens of well cited papers (in other sub-fields) -- once he seriously poked into the "loophole" he couldn't get published in any of the major journals, or get funding for experimental refutation of the quantum entaglement, and ended up taking early retirment from his tenured position out of frustration with, what he came to call, the "priesthood."
There is a classical entanglement between regular EM waves, which is formally identical to the quantum state entanglement for photons (as appearing in Bell's inequalities). There is nothing mysterious about that meaning of "entanglement," everything is perfectly local, computers made using them have no special powers (beyond what an analog computer would have, if one could build a usable one). Dutch physicist Robert Spreeuw (well known name in the optics of atoms) had worked out quite far the mathematical correspondence between the two formally identical phenomena, including the extensions to the so-called "quantum computing." So, in that sense, the "entangled" state has been produced many times, in quantum or classical systems.
What separates the "quantum entanglement" is the presumed ability of quantum entangled state to collapse instantly the remote subsystem state when a measurement is done on the other subsystem. To test that key property, on which the Quantum Computing contact with reality vitally rests, Bell inequality (or its more recent variations) is used. And that is where no test to date has come even close to being "loophole free." While papers and preprints may not emphasize or even mention the loophole, the fatal loophole is present in every single experiment. Merely showing that the state is consistent with the entangled state (which is how far the actual, raw, non-adjusted data ever goes) doesn't prove that it has the key property of remote subsystem collapse.
To prove that, the raw data would have to be used, before any assumptions about the missing data (inferred to exist from the triggers of some, but not all necessary photo-detectors, and which is routinely pressumed to obey the "fair sampling" hypothesis) are used to adjust the raw data (raw detector counts). Additional data adjustments are also done, specific to the experimental setup (especially common are subtractions of background counts, again under unproven and unprovable assumptions about unmeasurables).
Only after all the adjustments, the wishfully massaged data does violate (amazingly enough) the Bell inequalities (which is the objective if one wishes to prove the existence of quantum entanglement).
Having been once a theoretical physicist (and having written masters thesis in this area), I had corresponded over years, via mail and email with most experimenters who had published the "almost" proofs of the quantum entaglement. And when pushed, yes every one will tell you that indeed, there is a loophole of one kind or another, the hand put assumption about the missing data which makes the adjusted data violate the Bell inequalities. Without it, on the raw data, none violates the Bell inequalities.
To put it in plain terms for the non-physicists here, one could for example, having no data on where you were 1 minute ago, assume that you were 1000 miles away from your current place. And, say, now we can all find you on your current place reading this message. We're missing the data on where you were 1 minute ago (and there are no outside witnesses to say one way or another) but with our 1000 mile assumption, that seems pretty amazing how you managed to travel that far in so short time. Now we take for granted that you did travel 1000 miles in 1 munute, and then we start constructing ever more marvelous hypothetical technology based on that enormous speed for an earthly vehicle. Sure, you could come up with some pretty nifty transportation systems if you build upon that 1000 miles/minute vehicle you supposedly must have used. And if someone is going to pay us to do research on these possibilities, we're not going to pursue seriously the issue whether our key unverified assumption (your location 1 minute ago) might be wrong.
That is what the issue in quantum entanglement comes down to. Without making the unverifiable assumptions of certain particular kind (like that you were 1000 miles away 1 minute ago) about the missing data, nothing unusual or amazing can be deduced, the entanglement measured on actual data is no different than the classical one (which of course, can't collapse instantly the remote subsystem state).
There've been some experiments in Italy (so no ref) that have been running over the past couple of years (not "the 1980's") that have "proved" entanglement over very large distances (kilometres)
You probably mean Geneva experiments by Tittel et al from 1998-99; check on the Los Alamos preprint archive for their 10 km exeperiments. There is the group's email address at the top of the abstract, go ask them if the experiments were loophole free (they were not). Now, of course, they'll tell you stories and do the usual handwaving dance to convince you (if you appear in-the-know enough to be worthy their reply) why their unprovable assumptions were "natural" and why the "loophole" isn't likely to change their conclusions, should it ever be possible to do experiment without it. Yeah, sure.
And that is the bottom line. Just like with my "assumption" about your location 1 minute ago, I could dance and handwave all I want, why it is "natural" to assume, provided there are no witnesses to contradict me (i.e. data missing for good), that you were 1000 miles away, unless one can show without such assumption existence of the 1000 miles a minute vehicle, why should anyone believe it. Or fund it with their tax dollars.
When you peel off the layers of technical jargon and euphemisms (such as "loophole") protecting the dirty little secret and its priesthood's well being from the outsiders, that's the vital presumed "fact" on which the whole marvelous technology of Quantum Computing rests on -- the wishful assumption about the unmeasured, unmeasurable and irretrievably lost data points.
Extremely challenging, like in "it can't work and it won't ever work, but I hope the government and the industry sponsors won't find that out, at least until I retire, preferably after I am dead."
The whole field of Quantum Computing is a mathematical abstraction (fine, as any pure math is, as long as you don't try to claim that's how the real world works). Its vital connection with the real world is based on a highly dubious (even outright absurd, according to some physicists, including Einstein) conjecture about entangled quantum states (roughly, a special kind of "mystical" non-local correlation among events) which was actually never confirmed experimentally. And without that quantum entanglement the whole field is an excercise in pure abstract math with no bearing on reality.
While there were number of claims of an "almost" confirmation of this kind of quantum correlations (the so-called Bell inequality tests), there is always a disclaimer (explicit or, in recent years, between the lines as the swindle got harder to sell), such as "provided the combined setup and detection efficiency in this situation can be made above 82%" (even though it is typically well below 1% overall in the actual experiment; the most famous of its kind, Aspect experiment from early 1980s had only 0.2% combined efficiency, while 82% is needed for actual, "loophole free" proof) or provided we assume that the undetected events follow such and such statistics, etc. The alternative explanations of those experiments (requiring no belief in mystical instant action-at-a-distance), which naturally violate those wishfull assumptions, are ignored, or ridiculed as unimportant loopholes when forced to debate the opposition, by the "mystical" faction. After all, without believing their conjecture all the magic of quantum computing, quantum cryptography, quantum teleportation, along with funding, would vanish.
For those interested in the other side of these kinds of claims, why it doesn't work and why it will never work, check the site by a reputable British physicist Trevor Marshall, who has been fighting, along with a small group of allies, the "quantum magic" school for years:
Quantum Mechanics is not a Science"
Unfortunately, the vast bulk of the research funding in this area goes to the mystical faction. As long as there are fools with money, there will always be swindlers who will part the two.
For a more popular account, accessible to non-physicists, of the opposing view, you can check a site by a practical statistician (and general sceptic) Caroline Thompson:
Caroline Thompson's Physics
Like what? Write your congress-person? Vote for Al "The father of Internet" Gore (he is these days for "privacy," right)? Or go whine on messsage boards dedicated to "stuff that matters."
Maybe you should go live in a glass house, so anyone passing by can see you and your family, any time, anywhere and anything you do inside. If you're not doing anything "wrong" what is there to be ashamed of? After all, you could be hiding drugs in your tubby-time ducky, or you might be, while sitting on your potty, shuffling photos of nude underage girls in your left hand. If you have got nothing hide, why shouldn't all the good citizens and the good authorities be able to see you while you're in a tubby or on a potty?
(I guess, they must have stopped teaching word "privicy" in these enriched skoolz. Or maybe it is a dirty word now.)
Really, we can connect directly to Internet sites? Whoa! And different ones, too. Whooa squared. Thanks AOL, that's something. I knew it, if anyone could pull it off, it would be the genius of AOL.
I guess that must be the bad news part. Oh, well, nothing is perfect. "Cumbersome" is relative, anyway.
I would let them merge with TW-CNN, all the sooner they will both self-destruct. After all, looking at the Bell curve, there are only so many higher primates to the left of the moron line. (I guess CNET somehow managed to find one to write that story.)
One can customize here anything one can think of, and then some, when dealing with displaying the threads. That component is one of the better thought out than any I've seen. It doesn't seem beyond the current technology to have an extra checkbox on the customization screen to select small or large edit box. And if the author of this component really gets creative, some day we even may get the medium size option, too.
Now there is an elegant solution. Who would have ever thunk of that. Well, it is true, human is an adaptible animal, he can get used to anything if he applies himself.
It could have been in the attached MS Word .DOC file as well. And anyone who goes to ther MSDN site for various tech info, having to use IE with full ActiveX enabled to make the sites work right, is potentially infected. Or anyone using the MSDN Libraries, including MSVC Help, of recent couple years (which also don't work well without internet connection enabled).
Their whole "vision thing" of hypertext documents which seamlessly integrate your computer (via the MSDN Libraries, including compiler help files) into the Microsoft servers, reporting (if they wish so) anything you look up, any articles you read and for how long, anything you search for, which code samples you extract, ... even without coupling with ActiveX, is a virus/trojan handcrafted for industrial espionage, all by itself.
I wish only Bill Gates' machines and those of the other brains behind the Microsoft all-is-one (or is it one-is-all) "vision" got some of their own medicine.
BTW, I just typed in my first message in here, and this luxuriously spacious /. edit box with its eye pleasing courier font makes Microsoft Notepad seem like an ultra-ergonomic editor from the future. (The only cure for this is to make the web designer here use this exact edit box for three days for all of her editing work; by the second day the edit box would be twice as wide and three times as tall and user could set their own non-fixed pitch fonts. By the third day she would suggest dumping it altogether and using something like Userland's Manila editor .)
Now we know that not only does God play, he uses loaded dice !!
Although Einstein's view on QM is today a minority view, it was by no means disproven, experimentally or theoretically. While there were numerous claims of "disproof" of both kinds, it is now recognized that the theoretical claims (based mostly on von Neumann ideas from 1930s and Kohen-Spceker theorem of 1950s) are invalid. The experimental claims of "disproof" (based on tests of Bell inequalities from 1960s), while considered by the majority as very suggestive, all have fatal "loopholes" (euphemisms for "it almost worked").
Since there is no experimental or theoretical fact which would distingush between the two interpretations, there is no basis in claiming that great scientific successes of 20th century are based on the (present) majority interpretation (core of which is: intrinsic randmness, no local hidden variables, quantum state collapse or projection postulate). Nothing as yet follows from it which has any tangible/measurable consequences i.e. among others there is no quantum computing, quantum cryptography, quantum teleportation,... these are all wishful pipe-dreams (useful only in attracting funding from the ignorant and peddling quantum mysteries paperbacks).