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'Ingenious' Experiment Closes Loopholes In Quantum Theory
Annanag writes: A Bell experiment in the Netherlands has plugged loopholes in the theory of quantum mechanics using a technique called entanglement swapping to combine the benefits of using both light and matter. It's Nobel-Prize winning stuff. Quoting: "Experiments that use entangled photons are prone to the ‘detection loophole’: not all photons produced in the experiment are detected, and sometimes as many as 80% are lost. Experimenters therefore have to assume that the properties of the photons they capture are representative of the entire set. ...
[In the new work], researchers started with two unentangled electrons sitting in diamond crystals held in different labs on the Delft campus, 1.3 kilometers apart. Each electron was individually entangled with a photon, and both of those photons were then zipped to a third location. There, the two photons were entangled with each other — and this caused both their partner electrons to become entangled, too.
This did not work every time. In total, the team managed to generate 245 entangled pairs of electrons over the course of nine days. The team's measurements exceeded Bell’s bound, once again supporting the standard quantum view. Moreover, the experiment closed both loopholes at once: because the electrons were easy to monitor, the detection loophole was not an issue, and they were separated far enough apart to close the communication loophole, too."
[In the new work], researchers started with two unentangled electrons sitting in diamond crystals held in different labs on the Delft campus, 1.3 kilometers apart. Each electron was individually entangled with a photon, and both of those photons were then zipped to a third location. There, the two photons were entangled with each other — and this caused both their partner electrons to become entangled, too.
This did not work every time. In total, the team managed to generate 245 entangled pairs of electrons over the course of nine days. The team's measurements exceeded Bell’s bound, once again supporting the standard quantum view. Moreover, the experiment closed both loopholes at once: because the electrons were easy to monitor, the detection loophole was not an issue, and they were separated far enough apart to close the communication loophole, too."
Science doesn't explain why at all. How could it?
No number of cannonballs dropped off of towers will tell you why they fall.
A theory is a piece of supposition about the universe (normally dressed in mathematical formalism), backed up by observation. It helps us predict future events.
A mathematical description of what happens is exactly what one wants. If you cannot show anything, what happens and is not covered by the mathematical description, and you can deduct things what will happen, that wasn't known before, then you have a theory.
If you want an answer to the question why, you are not looking for science.
You're trolling, right? There's a big difference between the two things...
Even if the entanglement experiment didn't work every time, it did enough to demonstrate that it's extremely unlikely that the results can be explained through chance. There's nothing wrong with this.
Hopefully if someone else repeated the entanglement experiment, they'd obtain similar results. The criticism of psychology study was the inability to reproduce the study and obtain similar results.
Even most physicists don't understand Feynman's point that QM is called "mechanics" for a reason: it's a set of mechanical rules for getting the right answer. It tells you nothing about how the universe operates behind the scenes so as to produce the same answer as QM. Feynman's little easy-to-understand book on QED should be read by everyone who thinks that QM is more than a tool for performing calculations. (And read Tegmark's book for an example of what happens when an intelligent person reads meaning into QM.)
Regarding the actual article: at first sight, this looks like a great experimental verification of something that no one (as far as I know) doubted; but it's always good to confirm another prediction of QM that appears bizarre to us.
The difference is, that we are speaking here about a failure rate of singular events, which is a technical problem, and requires a larger population of events for sufficient confidence.
That is contrary to the results the previous article, that regardless of the population size, we cannot reproduce the result, which is a systemic problem.
"No number of cannonballs dropped off of towers will tell you why they fall."
Umm, gravity.
Why does gravity exist?
Does the fact that the two separated electrons are now entangled mean that flipping one of the electrons will now flip the other? Supposedly, quantum entanglement can't be used for communications but I've never understood why. Even if flipping one electron *might* flip the other, it means you could communicate because error-correcting protocols work pretty well over noisy communications channels.
And nobody understands how gravity works (we only understand the side effects of gravity).
"No, if you want "why" or "truth" look into the philosophy department."
Thats a bit defeatist. Science has always been about explaining the "why". Why is the sky blue, why do the planets going around the sun etc.
"Quantum mechanics describes a fucking ton of things"
It doesn't really explain anything. Its a convenient probabilistic bucket to put stuff in that we don't really understand but like to give it a name anyway.
"What" is for engineers. Physicists should always be aiming to answer the "why". Anyone can use equations, explaining why they work and where they come from is should be theoretical physics main goal, even if ultimately there's a level of reality we can't understand or progress beyond. No hand waving philosphers should be required.
That is contrary to the results the previous article, that regardless of the population size, we cannot reproduce the result, which is a systemic problem.
No. That is not how psychology works. It is not ethical to conduct psychology experiments on arbitrarily large groups of people. You cannot say that the experiment was expanded to a point where you can make a statement about it "regardless of the population size".
It is shameful that you were modded up for that comment, it shows how little people on slashdot understand about psychology.
Damn_registrars has no butt-hole. Damn_registrars has no use for a butt-hole.
What eludes us is the interpretation. Or in other words, we didn't find a way to fit this theory in our limited human minds. But the theory works, and it explains things, with maths.
The interpretation is important, but only because it makes working with the theory more intuitive and therefore allow us to progress faster. However, the true essence of any theory in modern physics lie in its mathematical description and how well it matches reality.
It's true that a model is not necessarily an explanation. Epicycles had predictive value (if tuned well), but almost all agree it's not how planetary motion "works". Newton gravity is considered a better explanation because it's the simplest working model: Occum's Razor.
If a better model comes along, we may make that the top model, ie, the "best explanation so far". Maybe there is no gravity, only something that happens to fit our gravity model. We do more experiments to find that out by testing the model more and testing alternative models.
Table-ized A.I.
The real reason for this barrage of science failures is how Slashdot responded to the proposition to teach people about the limits of understanding in each field of study.
A lot of people were posting and modding that Science should still be described as a collection of infallible knowledge for various reasons. So now we see the articles and studies pointing out how shit the processes and papers of all fields of science really are.
Large organized projects involving multiple people and intricate data tend to be shit, news at 11. Governments are the best examples of this but you also see it in corporations and not surprisingly science isn't magically exempt from the problems that occur whenever groups of people try to work together.
The real question is - exactly wtf is entanglement anyway? I can find lots to read about what it looks like and how it behaves... but what's the underlying mechanism? Is there even the most speculative explanation of it?
Things fall because of gravity. Thats an explanation. Why does gravity exist is another question entirely. There's probably endless levels of reality to go down through.
No. That is not how psychology works. It is not ethical to conduct psychology experiments on arbitrarily large groups of people. You cannot say that the experiment was expanded to a point where you can make a statement about it "regardless of the population size".
Wouldn't that then make it even harder still to reproduce experimental results, which only further erodes the status of psychology as a science? You only seem to be confirming his point. That ethical concerns are part of the cause is irrelevant. He was discussing effect.
It is shameful that you were modded up for that comment, it shows how little people on slashdot understand about psychology.
The more they understand about it, the worse it looks. It's too bad for you if you don't like that. If you have some interest in the outcome, for example if you yourself are a psychologist, it would be considered a minimal level of integrity to disclose that ... since we're speaking of ethics now. Oh further along those lines, I wonder just how much the field is influenced by the incredible profitability of prescription drugs? I bet that would be a fascinating research topic.
I usually describe this as the "flock of starlings" effect. ...
And usually there are plenty of posts explaining why this is wrong... you only ever reply to the ones that lack content though, claiming they don't give examples. Yet there are plenty of comments that give examples of experiments and situations that conflict with your posts that say nearly the same thing every time. As soon as someone actually takes the time to look things up or write things out, you ignore them
Electrons are also considered to be fundamental in physics *currently*, yet we have a dipole experiment that shows they are not fundamental particles.
Funny how your claims contradict physicists that don't see them as nonfundamental despite the same tests and include predictions of dipole moments...
The potential "for implementing device-independent quantum-secure communication and randomness certification."
What's difficult to infer is, did they essentially communicate at a distance faster then C? Are they getting better (more reliability and predictability) at creating a device that can communication at long distances 'instantly'?
Nobody knows. It just "has" to be that way.
A lot of quantum confusion can be dispelled by realizing that particles don't really exist. There are a bunch of phenomenae that look like particles, but also look like wavelike perturbations of a field. Since we don't really have any good mental analogies of what's "really" happenening, we have to fall back on mathematical descriptions. So the general concept is that you can glom two waves/particles together so that you cannot describe them individually any more. From my limited understanding, I don't think there's a mechamism so much as it's inherent to quantum mechanics to be able to construct systems like this.
Actually it's the same thing, the ability to reproduce results. So it's a far comment. The author is jumping to conclusions. One experiment proves little. When others replicate, if any do, they you have something.
I take a photon, I split it into two identical photons
Do you? That's very clever of you. People have won Nobel prizes for less.
I usually describe this as the "flock of starlings" effect. If all you can see is a flock and not the individual bird, the flock appears to jump and leap and disappear and reappear. But it is simply the effect of a detector that can only see flocks and not birds.
Yes, you do keep describing it that way. And you've been told several times why you're wrong, but you just won't listen.
However protons are not fundamental particles anymore, deep inelastic scattering showed they are made of smaller particles. So you never detected the proton AT ALL, you simply detected the net result of the effects of these sub-proton particles. That net result jumped around, not the proton. Likewise you could not have 'set' the position of the proton, because it does not exist! It was just an effect of multiple smaller particles on the detection mechanism.
Okay, let's ignore the fact that you're just plain wrong. Why do electrons, which are fundamental particles, behave the same way?
systemd is Roko's Basilisk.
Fuckin' magnets, how do they work?!
Look up the definition of science some time then post a comment. Hint, science isn't determined by the subject one studies but by the methods one uses.
Same thing on every quantum mechanics story, and the only reason it doesn't get torn apart every time is because people get tired of making the same debunking replies. After making detailed counterpoints and seeing no response or change, there isn't much motivation to waste more time. But keep on posting, because on Slashdot if you say it enough times it becomes true and upmodded if you can outlast opposition.
Quantum mechanics explains chemistry, how atoms bind together to form molecules. You call that nothing?
The fact that you can predict from first QM principles that CH4 is a stable molecule, and OH4 is not (but H2O is) is well beyond a "probabilistic bucket" I would say.
I have a BA in philosophy and I took as many courses as I could on science and epistemology. The general concensus in these fields (of course with some disenters) is that you will always be able to ask this question about anything once you reach the scale boundries of our knowledge. When we say "gravity", what we really mean is a collection of rules which we are able to consistently produce accurate predictions from when applied to our observations. We can describe how a waterfall works in terms of gravity, but then when we ask how gravity works we must defer to some other system which then itself we will need to explain in terms of something else etcetera. I once grilled a chemist friend on what he meant when he said "electrons will always try to such and such" and he was stumped. It wasn't fair, because really the questions I was asking were based on a false appreciation of what the human study of natural law is able to be. Entanglement is a set of circumstances which we observe under certain conditions and believe are related to the point that we can give them a name. So are an apple, rugby, paint thinner and pornography. It is our own need for certainty that makes it difficult for us to accept this limitation of language and meaning.
yep, and they replicated their result 245 times. The typical psych experiment doesn't have that luxury; it takes too long and too much effort.
indeed, hypothesis tested by experiment. But lack of reproducibility calls into question the effectiveness of the testing.
It's been about explaining the "why" questions that really translate to "what's happening that results in this phenomena".
Gravity exists because spacetime, curved by massive bodies, effectively changes what it means to have inertial reference frames from the more intuitive Newtonian notion. Take away the massive bodies and spacetime flattens, straight lines are Euclidean, and gravitational attraction goes away. Gravity, then, exists due to the interaction between mass and spacetime.
Of course, you could ask why that interaction exists, and keep asking the question as more explanations are found. I don't know that that'd ever end, but I guess you could eventually hit some inherent axiom or self-referential property of nature. If you're asking for some ultimate underlying conscious intention, though, you may find yourself disappointed, or at least you should accept the possibility that such a question may simply not apply.
"Is not a sentence" is not a sentence. Well damn.
Look up the definition of science some time then post a comment. Hint, science isn't determined by the subject one studies but by the methods one uses.
Rather than making childish snide remarks (welcome to the net, eh?) try to understand what I am actually saying.
Reproducing the results of a scientific experiment using sound methodology is the only way to confirm that those results are valid. If those results cannot be reliably reproduced, then what you have is an idea or a philosophy, not a science.
It's the same reason phrenology was abandoned after being recognized for the pseudoscience it really was. There was no ability to reliably and repeatedly demonstrate its alleged findings. That's exactly what distinguishes science from pseudoscience. The "subject one studies" is immaterial, and I question your honesty for pretending like anyone was claiming otherwise.
There is no necessity that reality consists of endless levels. There can be a "rock bottom" of existence that just "is", and cannot be explained.
If it cannot _ever_ be explained, not by any level of understanding and technology, then you're really just using a non-traditional description of theology.
Science has never tried to explain the WHY. Science is about the HOW. That's a fundamental staple of the scientific method. Once we understand HOW science is basically done. This isn't to say science won't find some answers as to "WHY" but that's not the goal.
The mathematical theory we call quantum mechanics does an incredible job of describing the HOW. And lets not pretend this is just some idea someone dreamed up one night, this is a mathematical theory that was put forth decades before we had the ability to test any of it.
We now have the ability to test it, and the theory is passing each and every test, the results we see in labs are the exact results predicted by the theory.
Gravity is a theory. The theory doesn't ask WHY and doesn't attempt to answer it, what it does do however, is explain HOW gravity affects us and provides repeatable, and falsifiable tests we can run against it. We've proven gravity exists, it's a basic fact and life on this planet requires it, because we were evolved within the system that has gravity.
WHY does gravity work as it does, and what is the underlying mechanism? We don't know, but if we have any hope of knowing, it will be quantum physics that explains it.
The Higgs for example, yes I know that's still arguable, but the THEORY makes sense and if we have indeed found evidence of the Higgs, the theory was right. Mass doesn't actually exist, mass is the resistance offered by the "ether" as objects move through it. This changes everything, if we can prove we've found the Higgs.
The problem with WHY is that the goal posts are static, we can never get a definitive answer because science doesn't really do "absolutes", science does 99% sure. Why did the planets form as they did? We answered that by discovering the HOW. But then, the why becomes why is the universe built in such a way to have these natural laws? We can't answer that because we live in this universe and simply can't fathom one with different laws of nature.
The WHY is left to philosophy until we can uncover enough of the HOW to explain away any silly WHY questions.
Quantum entanglement is real, testable, repeatable, and falsifiable. Just because we're not at a stage that we can explain the underlying mechanisms, doesn't mean the theory is wrong.
Beyond that, just because you can't find this information doesn't mean it's not out there, google is NOT the be all end all source of information, and in relation to quantum mechanics and more to the point, entanglement, this is still a fresh field. I suspect that if you ACTUALLY wanted to understand it, you'd buy some of the same books I did and actually read them.
In short (haha I know) Quantum mechanics explains fucking reality, I'm not sure how much more "explaining" you need.
I have a BA in philosophy and I took as many courses as I could on science and epistemology. The general concensus in these fields (of course with some disenters) is that you will always be able to ask this question about anything once you reach the scale boundries of our knowledge. When we say "gravity", what we really mean is a collection of rules which we are able to consistently produce accurate predictions from when applied to our observations. We can describe how a waterfall works in terms of gravity, but then when we ask how gravity works we must defer to some other system which then itself we will need to explain in terms of something else etcetera. I once grilled a chemist friend on what he meant when he said "electrons will always try to such and such" and he was stumped. It wasn't fair, because really the questions I was asking were based on a false appreciation of what the human study of natural law is able to be. Entanglement is a set of circumstances which we observe under certain conditions and believe are related to the point that we can give them a name. So are an apple, rugby, paint thinner and pornography. It is our own need for certainty that makes it difficult for us to accept this limitation of language and meaning.
I appreciate your explanation. On the one hand, it almost sounds hopeless because the rabbit hole is bottomless, but at least we can enjoy increasingly more effective technology along the way. On the other, I can now rephrase my question thusly: "in terms of what other system could we try to explain the observed phenomena that we call entanglement?" Specifically (while I realize it cannot be used to transmit information), how is it faster than light? Is the concept of locality a defensible one?
...the electrons were moved between labs on a bicycle.
Ah, the Dutch! Whether it is a dike or a quantum theory, they can plug the holes ;-)
Unfortunately I'm not at all equipped to answer those questions, and I hope that somebody here is. The one thing I can contribute is that it is theoretically possible for us to develop an internally consistent system of natural laws which both fit and predict all observable phenomena. If that were to happen then the question of what explains (or "causes", a term fraught with complication) that system would be purely academic and almost certainly unprovable, since we would already have developed the ability to predict and explain anything which we might use as a subject for experiment. Quantum physics may be on the edge of such system. It would be cooler if it wasn't though :p
"Newton gravity is considered a better explanation because it's the simplest working model"
Yes, and no. The simplest has a certain charm to it, but that doesn't make it more correct. What makes a theory more correct, aside from predictive value, is how well the elements and relationships of the theory correspond to elements and relationships of the physical system.
To borrow, and mangle, a quote from B.W.:
"Psychology is not rocket science. Hell, it isn't even sociology."
Will
Gravity is not just an explanation-- it's the LAW.
Who is RTFM and when will he help me with Unix?
"in terms of what other system could we try to explain the observed phenomena that we call entanglement?" Specifically (while I realize it cannot be used to transmit information), how is it faster than light? Is the concept of locality a defensible one?
Interestingly enough like most effects of quantum mechanics, entanglement does not have an easy macroscopic analog to compare. One way to think about it is that it is a type of emergent behavior because of the rules that QM appear to follow.
More specifically, entanglement is kind of emergent behavior that is a logical consequence of conservation rules and quantum superposition states. If you believe in the QM rules regarding conservation (e.g, conservation of say spin), and QM rules involved with superposition wave function collapse (e.g., so called "observation"), the emergent consequence of these rules is a behavior we call entanglement.
The macroscopic analog is sort of as follows. Suppose you have 1 balls and 2 boxes. By some method hidden from you, the ball into one of the two boxes and it is sealed. If you believe in conservation of balls, The two boxes are now entangled. You can move them arbitrarily far apart and then open one box, if it has a ball, you instantly know the other doesn't have a ball.
Where this breaks down is how you put the ball in the box. In the QM version of this, the method of which you put the ball into the box doesn't really put the ball into the box, it simply puts a type of probability of a ball into a box. Interestingly enough, the box can act sort of like a 1/2 ball in the box until you open it and then it "collapses" and is either a ball or not ball. The strange part is how can it act as if there is a 1/2 ball in the box before you open it? If you think of the decision being made when you seal the box, there is some sort of locality, but if you think of the decision being made when you open the 1/2 filled box, there is non-locality and you need to use a concept like entanglement as an emergent behavior.
That is 1/2 ball in the box (part particle, part wave) is QM and nobody really understands that part, so there's really not an analogous macroscopic system on which to understand it, because the systems we are familiar with don't follow those rules.
On the concept of locality, it's really unknown. We generally think of distance and time (warped by general relativity) as the way we measure locality (e.g., light cones, etc), but there isn't a clear idea if there isn't a macro-dimension or holographic way that alters our understanding what is local or non-local. Using current theories, we already speculate that there are singular violations of locality (e..g, EPR's or worm-holes, etc), and we don't understand the fabric of space-time (e.g quantum gravity) well enough to say if our current theories about this are descriptive enough to yield our current intuitions about space-time locality or if it will be as weird as QM.
On the other, I can now rephrase my question thusly: "in terms of what other system could we try to explain the observed phenomena that we call entanglement?"
Math. Specifically, complex linear algebra.
obvious troll is obvious.
entropy happens
I don't get it. I thought the loopholes in classical mechanics is the quantum mechanics. If you close the loopholes and make it deterministic, then you are back to Newton, baby! Its all canon firing balls horizontally but what would happen if due to curvature the earth surface falls more rapidly than the canonball.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
Guys, this is huge. People have been doing versions of this experiment for decades, every time making it more refined, in order to be able to reach the striking conclusion with the fewest possible assumptions: that the world is not deterministic. The quantum randomness is not our ignorance, is a fundamental property of nature.
What they did was to violate a Bell inequality, without using the most questionable extra assumptions (called loopholes) people normally use to extract a conclusion from this experiment: that the separated laboratories are not somehow communicating to conspire to produce the desired outcome, or that the photons they detect are indeed a good representative of all the photons that were emitted in the experiment (normally people can detect only a small fraction of the photons).
I am a quantum physicist, and I know the science behind this experiment very well. If anybody wants to ask me anything, I'd be glad to oblige.
entropy happens
"Entanglement" is a philosophically difficult arena. According to quantum theory, there is just one wavefunction for the entire Universe. However, we as observers are part of that wavefunction observing another part of that wavefunction with a really, really, big chunk of the whole wavefunction effectively unobservable but still coupled to the observer (part of the wavefunction), the measuring apparatus (part of the wavefunction), and the "experiment" (yep, part of the wavefunction. Everything is "entangled", but quantum mechanics also predicts that large systems approximated with a random phase condition will behave like a classical system, and the usual rule is that we treat a measurement apparatus as a classical system that breaks the entanglement of a measured systems and forces it "unpredictably" into a separable state. But even this is words, not equations although random phase approximations are indeed equations and are used frequently in field theory.
The only coherent explanation of this that I am aware of is the process of:
a) Starting with a density matrix (or other representation) for "the Universe".
b) Use the Nakajima-Zwanzig approach of splitting the (fully entangled) density matrix up into two parts -- a "system" that you will continue to treat as a quantum system, and a "bath" -- everything else -- which would also include the measuring apparatus if you were trying to describe an experiment. One then accepts the fact that one cannot know or prepare the state of the bath (which is really, really big being the rest of the Universe and everything) and so one makes a statistical approximation of the bath (taking the trace) which essentially eliminates the pesky entanglement but also breaks useful things like unitarity and in a sense, conservation laws. One them creates projection-valued operators and transforms the equations for the system into stochastic or semiclassical equations of motion.
c) IIRC your final result is quantum mechanics for the system expressed as a non-Markovian integrodifferential equation that is almost impossible to solve. However, if one makes a Markov approximation (forces it to be time-local, delta-correlates time) you end up with a decent explanation for things like spontaneous decay as an "exponential" process rather than a punctuated unitary process. You go one way, you can make it into a Langevin equation, go another you can make it more like Fokker-Planck.
The lovely thing about this approach is that it renders moot all sorts of nonsense, such as EPR paradoxes and "wavefunction collapse". It is perfectly clear that in the Universal wavefunction no such paradox or collapse can occur. They are simply expressions of our ignorance of phase and state whenever we try to isolate some part of the whole and pretend that it is a standalone "system" that can ever be decoupled from everything else. Schrodinger's cat paradoxes disappear as there is no paradox in the Universal wavefunction, only when we try to project the state of the cat against our ignorance of phase and interaction with the outside Universe. The cat, if you like, cannot be entangled separately from its preexisting entanglement with the rest of the Universe, and we only get into trouble when we have to force it by partitioning the system in order to get a chunk small enough to work with.
Hope this helps. I doubt it will. Very few people seem to be in touch with Nakajima-Zwanzig and the Generalized Master Equation these days, and don't treat problems like this as OPEN quantum systems as opposed to closed systems with a classical measurement apparatus, which is a place you only get to on the far side of the N-Z GME ritual.
rgb
Even when the experts all agree, they may well be mistaken. --- Bertrand Russell.
This experiment has a big problem, as an applied optics (polarization specific) expert, they use polarization entanglement, but then run the light through fiber optics.
The problem is that fiber optics (even polarization preserving designs) have a terrible issue with preservation of polarization states.
I haven't read the paper in detail yet, but I don't know how they can mitigate this issue...
The real question is - exactly wtf is entanglement anyway? I can find lots to read about what it looks like and how it behaves... but what's the underlying mechanism? Is there even the most speculative explanation of it?
Here's the best answer I can give you - I think it's true, and not so over-simplified as to be wrong.
The universe has some underlying state. We don't have direct access to that state - not only is it not directly observable, it's not directly related in any intuitive way to the state we can observe. There's this arbirtary-seeming transform between underlying state and what we observe (it only seems odd or arbitrary because all our intuitions are based on human-scale observables, and are not at all directly informed by this underlying state). This underlying state seems to be well-defined and deterministic, forwards and backwards in time. The observable universe is not.
Entanglement is a feature of how observations relate to underlying state - a feature of the transform. In very simple experiments we can measure specific properties of, say, an electron. We can't measure all of them, for a given electron, because the transform just doesn't work that way, but we can measure some. However, that's deceptive, because you can't really track that property of that electron over time, in non-trivial cases. If e.g. two electrons interact, become entangled, your observations are now a function of both electrons' underlying state, and that's a different transform from 2 non-entangled electrons.
There are two key concepts here. The first is that the whole notion of "particle" is a handy but false oversimplification. It can lead you to all sorts of false intuitions about how particles behave. Fundamentally, individual e.g. electrons don't have unique identities. The underlying state is a single electron field, which other fields can interact with, in a way that can sometimes be simplified as "particle interactions", for a simpler mental model, but you can't go too deep with that model. An example: "two electrons collide in an accelerator, and two electrons leave, which is which?" That question is "not even wrong", it's just nonsense. Thinking of electrons as billiard balls colliding is simply not a helpful model, as it just misses the point of the interaction.
"Entanglement" happens just when the "particle" mental model fails: you can no longer pick two disjoint areas in the electron field and consider them as independent "electrons", but instead you have to reason about two areas which may be quite disconnected in space and time. E.g., you might know for sure that one electron is spin-up, and one spin-down, but have 0 information about which is which. None of that matters to the underlying state: there's just one electron field, and the only truly correct way to reason about it it to reason about the whole field all the time, and so this is only half of "WTF is entanglement".
The second concept gets too much into the math to explain well, but in a hand-wavy way it's this: "what is measurement?". There are older interpretations about measurement causing wavestate collapse and so on, but they're wrong because of that word "cause". Measurement is simply the observer becoming entangled with the observed. Measuring one entangled electron doesn't "cause" the other electron to do or become anything. The underlying state is unchanged, which is why there's no faster-than-light effect. In some cases, this is an overly pedantic distinction, but it matters when the difference between QM and intuition matters. In a two-slit experiment where you see an interference pattern at your detector, if you add a measuring device to one slit suddenly you don't see that interference pattern. Informally we might say the second observer "caused" this change, but formally that's wrong, it's just that a system with 2 slits and 2 detectors behaves differently from a system with 2 slits and one detector, and it doesn't matter which detector the electron passes first, because (see above) an "electron" as a discrete particle is fiction anyway, and both detectors are entangled with the electron field already, or they couldn't measure an electron anyhow.
Socialism: a lie told by totalitarians and believed by fools.
If we modify this situation just slightly, it seems to give FTL communication. Here's how we modify it. Instead of electrons 1 and 2 being 1.3 kilometers apart, we put them in the same room, "room X". And we don't have just one electron, but instead very many. We put the "third location" very far away. Perhaps light-years away. At the third location, we decide whether we want to send a '1' or a '0'. If we decide to send a '1', we entangle many of the photons, which entangles the electrons in room X. If we decide to send a '0', we don't entangle anything. At room X many light-years away, we detect whether the electrons are entangled or not. This is detectable, correct? Doesn't this allow us to receive a '1' or a '0'? Don't we now have FTL communication? What am I missing?
If they could only get some of the photons to entangle, then how do we know that the ones that would not entangle were not due to the state of the original electrons. If the electrons are in opposing states, then when you entangle a photon with it and try to entangle it with another photon that has been entangled with the other electron, it will refuse to entangle unless the two electrons are in a compatible state. I don't think you can leave out the failed to entangle photons like that. It seems that they tell you something important about the system.
-- ssoorrrryy,, dduupplleexx sswwiittcchh oonn.. -Quote found on actual fortune cookie.
Does this open the door up to FTL communication?
Science & open-source build trust from peer review. Learn systems you can trust.
OK, I'll bite. You said in your post that the world is not deterministic. Does the new experiment disprove superdetermism?
Just to show where I'm getting this from I did glance just now at the wikipedia article on Bell's theorem and, I quote:
Even though I don't get a lot of this stuff, I do sort of think I get the idea that if things were superdeterministic, like we're all somewhere in a pattern created by a rule 110 machine or something, that there would be no need for either instantaneous communication or a hidden variable in order to have 'entanglement'.
In theory, theory and practice are the same; in practice they're different. (Yogi Berra & A. Einstein)
You seriously invoke infinite regress?!
You're not the only one doing that on this thread, but seriously, what a bunch of stuffy, staid minds. You mights as well say "We don't like such impertinent questions!"
I'm not sure I consider those replications, as they are all using the same equipment, and if there were a systematic problem, then there might well be a systematic effect.
OTOH, this is, essentially, a replication of experiments done previously, with a couple of added features, and it's results are consistent with those prior experiments. *THAT* I do consider a replication.
Given the nature of publishing, the study that confirms this one will also need to have some changes. It shouldn't be that way, but journals won't print *mere* replications, you've got to have some extension.
I think we've pushed this "anyone can grow up to be president" thing too far.
There *are* interpretations of quantum mechanics which *do* explain the "meaning" of the equations. (I'm guessing that's what you mean by "why".) Unfortunately there are several different interpretations that are consistent with the math. My favorite is the Everett-Graham-Wheeler multiworld model, but it's not the only alternative, and so far there seems to be no way to choose between them. But there are only a few interpretations, so most possible ideas of how things could work, and what it all means, are incorrect.
E.g., if you hypothesize that some god is running things, you need to presume that he's systematically interfering with the experiments (or that he just created the universe 3 seconds ago complete with all internal evidence of consistency). If you do, that is consistent with quantum theory. But it's not a very useful interpretation, as it doesn't allow you to make any predictions. Another useless theory is "When the universe happened to come into being, it was set with a series of values that specify everything that is ever going to happen down the the sub-atomic level from the first instant of existence until the final end. That can be made consistent. (Actually, that one is useful if you combine it with a theory that the simplest possible set of constraints was used.)
The multiworld hypothesis basically says that the universe splits with every quantum interaction, and you move forwards into all of the results with a probability density that reflects the probability of the quantum events involved. At the high level that we interact with things that translates into "an honest die has a 1/6 chance of coming up with a 6". So it's one of the useful interpretations. And the Copenhagen interpretation basically says "Shut up and calculate. No explanation is possible.". Most working physicists prefer the Copenhagen interpretation, because it makes things simpler (without changing the math). There are others. Look up "implicate order" for example.
I think we've pushed this "anyone can grow up to be president" thing too far.
Sorry, that's Newtonian. Einstein's gravity exists because mass warps space-time. Now as to why it does that.....
I think we've pushed this "anyone can grow up to be president" thing too far.
Actually I worked for awhile on a variation of that, but it depends on the presence of mass slowing time, so that particles experience a slight preference to end up in slower time than in faster time. You've got to rewrite the equations to describe space as flat, and all the bending to be handled by variations in the speed of time (WHAT???, but yes). I was assured that this was a reasonable and valid thing to do. I never did learn enough quantum theory to try to convert this into a general theory of gravity, but I think it would work.
But that's just mechanism. Mechanism can't answer "why?". Why demands an agent with a purpose. So the real answer is that English doesn't properly describe the universe, and implicitly attributes to various things characteristics that they don't have. (It may not just be English, perhaps it's a part of the essential human thought process. That kind of assumption could be an asset in detecting a lurking predator.)
I think we've pushed this "anyone can grow up to be president" thing too far.
I need clarification of that. There are no "elements" in Newtonian gravity. Epicycles can be quite accurate if enough "layers" are used. Think of it as "circular regression".
Table-ized A.I.
I think the answer is "we don't really know." One of the criticisms of the standard model is that, although it has fantastic predictive ability, it doesn't have much explanatory ability. It can't even tell you something as seemingly simple as why an electron has the rest mass that it does.
However, you might find the phase/state/configuration space formulation of quantum mechanics more intuitively satisfying. You can imagine a quantum system as being a particular state space with rules restricting how you can move.
Maybe some new developments, such as the holographic hypothesis, will provide more explanatory power.
I'm intrigued by the elimination of the word cause to which you allude. I like this very much because it fits in very well with the philosophy. If you ask somebody what the word cause means they will only be able to give you similies of the word cause, but nothing else that stands up to scrutiny. They might say "well, it's a factor without which the event would not have taken place", but then it is clearly in defiance of what we want to say for me to claim "I drove to Ottawa yesterday because there are roads. I couldn't have driven to Ottawa without roads, but neither did I drive there because there were roads. A set of circumstances existed under which me driving to Ottawa was an event that was going to happen. From your description, entaglement appears to be a way of replacing cause with sets of circumstances that only care about the entire state of the system. Cool!
This is true, superdeterminism is a way out of the conclusion of the experiment.
That is why I said they only did the experiment without using "the most questionable extra assumptions". The assumption that the world is not superdeterministic is very reasonable, IMHO. Without it, one cannot even do science. For example, in a superdeterministic world, the wavefunction of a photon will depend on which measurements you are making on it, so there isn't such a thing as "the" wavefunction of the photon, and it is not possible to learn anything about it. It is this kind of conspiratorial correlation that superdeterminism uses to produce the violation of a Bell inequality. For me, it's insanity on the level of Last Thursdayism: logically consistent, unfalsifiable, and nobody will ever take seriously.
But I'm troubled by your last sentence:
that there would be no need for either instantaneous communication or a hidden variable in order to have 'entanglement'.
We don't need this stuff to have entanglement. Entanglement is just a property of Nature, it's there whether you want it or not. What we need instantaneous communication for is to create the appearance of entanglement in a hypothetical world that would be classical (or, technically speaking, has hidden variables). Since our world is quantum, this is of no concern.
entropy happens
Your "underlying state" seems equivalent to a "hidden variables" theory. Note that the Bell inequality says that if the universe is local (no action at a distance, special relativity, etc.) then hidden variable theories cannot reproduce the observations of quantum mechanics.
It's possible the universe really does have a deterministic nature that is hidden from us, but if that's true then the laws of physics are not local. We tend to shy away from that option because of the success of special relativity, and prefer the other: that the universe really doesn't have a deterministic underlying reality.
Wow. +1 "Enlightening".
No, your children are not the special ones. Nor are your pets.
You're mixing up generally irreproducible results and a situation where a proportion of reported results are not replicated.
Modern psychology is very much a science, using the scientific method. However, due to the difficulty of studying it, the requirements for publishing a result are low enough that many of them turn out to be incorrect (not reproducible). That these results are eventually found to be incorrect is a validation of the scientific nature of psychology.
ANY subject involving a complex, difficult-to-study subject is going to have the same problem. Most fields like that, psychology, medical science, ecology, systems biology, etc., prefer allowing reasonable sized studies (usually less than a few million dollars) to be published, knowing that they may be incorrect, then replicating the interesting ones. Particle physics has tended to go the opposite way, where high profile results are not published until the confidence is very high, but those results also cost billions to achieve. Lots of less high profile results are, of course, held to lower standards.
The real lesson to take from the problem of replicability is not snide "psychology isn't a science" but rather that being published in a journal (hopefully) means that the study was done in a scientific way, but is no guarantee that it's true.
Locality doesn't work. These experiments can be done with electrons, and we can measure the spin. If one electron has spin up, the other will have spin down if measured along the same axis. If the measurement axes are different, you can calculate how likely one electron is to have spin down if the other measures as spin up based on assumptions. It turns out that the observed probabilities don't match the ones you'd get if they had what you'd expect if the relation was based on locality. Look up Bell's theorem.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
Entanglement may actually have a macroscopic analog, just not one we have experienced yet. Spend some time Googling the "ER=EPR Conjecture".
The TL;DR is "entanglement and wormholes are different manifestations of the same underlying thing"
You can get a very limited idea of entanglement by thinking of two envelopes, one red card, and one black card. If you put one card in each envelope, you've got envelopes entangled in the sense that if you open one you know the color of the card in the other, wherever it may be.
Now, we figure that we can open the envelopes in different ways with different but related results (if we open them at the bottom, the cards change color, and if we open right along a side it's random which card is which color, and it gets more complicated), that we can open the envelopes differently (one at the top and one at the side, for example), and that we can influence the probabilities by opening the envelopes in certain ways that aren't explained by the original state of one black and one red. This is where it gets complicated.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
There are sciences where we can't conduct experiments, astronomy being the obvious one. Hypothesis tested by observation includes these.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
Gravity is inertia through curved spacetime. It happens that mass has a local effect on spacetime that distorts geodesics.
And now, all together...
What's inertia, and why does it happen like that? What's spacetime? What does it really mean for spacetime to be curved? Why does mass curve spacetime? What is mass?
You can get at least partial answers to some of these if you ask somebody who knows more than I do, of course.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
Theology isn't an experimental science. Physics is. We can be sure that something works in physics even if we don't understand it. How are we supposed to be sure that anything in theology works in the real world?
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
The difference between quantum mechanics and just any convenient probabilistic bucket is that it has excellent predictive value. Using the known principles of quantum mechanics, we can calculate what we'll observe in all sorts of experiments, and the experimental agreement is extremely good.
As it happens, there's a lot of numbers that are vital in making these predictions, and there's a lot of them with no obvious relation to each other, which look completely arbitrary. In science, when we learn something, it usually leaves more questions. That's what makes it fun.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
our "underlying state" seems equivalent to a "hidden variables" theory.
No, it's just the sloppiness of English trying to represent math, or perhaps my lack of facility with one of those in trying to craft a metaphor.
To extend my above metaphor: there's no hidden "observable" state. The underlying state is not "this one spin-up, that one spin-down" (which is forbidden), because there are not electron identities anyhow, but instead "exactly one of them is spin-up". As you measure one of them, there are now three entangled things: the two electrons and your detector, and there's a set of allowed observables given all that, when you add the second detector, now there are 4 entangled items. It's not non-local, it's just a constraining of the set of allowed states for the complete system.
Socialism: a lie told by totalitarians and believed by fools.
That's probably a better phrase, I agree. While the definition of "experiment", as I understand it, does include "set up a telescope and see what's there" (being "an act for the purpose of discovering") the common perception includes setting up equipment to ensure that what you're watching turns out to be interesting :)
It can be invoked to discourage any question, and I don't believe that it should stop us for looking for answers. However, there is no point in denying a logically true fact. In my view the only way to be both intellectually honest AND productive is to say "I will never be able to fully explain anything, but the more I can the better".
Everything in physics works in both time directions (you have to swap some signs +/- when you reverse time, but it all works). Causality as "a chain of related events over time" is a real thing, even if what you place in the chain may be somewhat arbitrary, but the direction, which is cause and which is effect, isn't so well defined. At the QM scale it's arbitrary. In human experience, a film played in one direction looks different than in the other because, ultimately, of the energy input from the Sun breaking the symmetry.
Socialism: a lie told by totalitarians and believed by fools.
Bell's inequality shows that both local hidden variable AND stochastic theories cannot reproduce the observations of quantum mechanics. Bell's theorem showed that the universe is non-local, regardless of your preferred interpretation. Bell himself promoted a pilot wave interpretation.
Many people have misunderstood Bell's result to be saying something against hidden variable theories. It isn't. It is saying something against locality.
Hmm, now that's a comment that troubles me a bit. Somewhere in this discussion somebody said that Richard Feynman (Ironically, I'm reading Surely You're Joking Mr Feyman right now.) said it's called Quantum Mechanics because we don't really understand it, it's just some mechanical rules. Your description of entanglement seems to be the same thing. I think scientists are like kids who always ask 'why'. Everytime their parents give them an answer, they ask 'why'. They're still asking 'why' about entanglement. If it turned out that everything was superdetermined, then they'd be asking 'why' to that as well.
What follows is a train of thought I've had when reading philosophical stuff and watching things like "Closer to the Truth". It isn't my personal 'belief', I'm way too agnostic to have such a complicated 'belief', but I think it might be appropriate to throw it out here:
This superdeterminism smacks of predestinationism, which is a religious notion that troubles people over the 'free will' question. To my mind, if it turned out the universe was a giant computer running a deterministic program, it wouldn't make us 'predictable', because the only way to get ahead of the Universe's own CPU clock would be to have an even bigger, faster computer than the whole universe. The future is set the same way the past is set, it just hasn't become the past yet for us. Phyiscist types are always talking about space-time, and how one observer can 'see' the future of another. Maybe it is all one big lump, Past, Future, Present, but living through it is still life, isn't it?
In theory, theory and practice are the same; in practice they're different. (Yogi Berra & A. Einstein)
It is shameful that you were modded up for that comment, it shows how little people on slashdot understand about psychology.
The more they understand about it, the worse it looks.
Quite the opposite most of the time. A big problem here is that a lot of people (particularly people on slashdot, though this happens in many other circles as well) think they know a lot about psychology because they have read a lot of angry rants against it, even though they have never had formal exposure to the fundamentals or history of psychology.
If you have some interest in the outcome, for example if you yourself are a psychologist, it would be considered a minimal level of integrity to disclose that ... since we're speaking of ethics now.
I am not a psychologist. I have friends and colleagues who are, and I took psychology as an undergrad. My work is in a more contemporary hard science.
It is noteworthy that you call up ethics here, when earlier in the same comment you said
That ethical concerns are part of the cause is irrelevant.
Nice of you to so consistently show concern for ethics.
Oh further along those lines, I wonder just how much the field is influenced by the incredible profitability of prescription drugs?
Last time I checked, few states allow psychologists to write drug prescriptions, that job is usually left to (medical school trained) psychiatrists (wikipedia shows only three states grant that ability to psychologists in the US). Psychologists have little to gain financially by encouraging pharmacological treatments for their patients.
I bet that would be a fascinating research topic.
The most commonly prescribed (in terms of patients who have had it prescribed to them) drug for mental health use is Prozac, which has been available generic for some time. Once a drug has become available generic, the profit is nearly gone. If you want to look in to the prescribing rates of new drugs for mental health versus other health conditions, and compare which are prescribed more quickly, that may indeed be an interesting topic. Your bias is so evident here though that I would be shocked if you were to ever attempt to undertake such a study.
Damn_registrars has no butt-hole. Damn_registrars has no use for a butt-hole.
See, what you're missing is simply that it's turtles all the way down.
I've fallen off your lawn, and I can't get up.
Certainly not. Since psychology doesn't work. Period.
I've fallen off your lawn, and I can't get up.
European starlings, or African starlings?
I've fallen off your lawn, and I can't get up.
You are coming upon an old conundrum. Does every particle "know" about every other particle or not? How does a rotating reference frame know it is rotating? The side that you are taking will be disproven if gravity waves are found. That is a vast oversimplification but I think the question is still open. I am willing to be corrected.
The Bell's theorem is based on the assumption that if there are local variables that are hidden, the result measured spins of the particles would be linearly correlated to the angles these particles are created from.
I do not see how this assumption is valid though. Particles are not billiard balls. Particles may have properties that force their spin into specific correlations. It is stupid to accept that local variables would mean linear correlation.
particles experience a slight preference to end up in slower time than in faster time
That's what refraction does for rays and waves, always turning toward the slowest direction. Is that any help? Can you give any references? Your work sounds interesting.
And to respond to the initial question - gravity exists because we agree on the narrative.
--
Your ideas are intriguing and I wish to subscribe to your newsletter.
No. That is not how psychology works.
Certainly not. Since psychology doesn't work. Period.
It is a safe bet that if you are willing to make such a sweeping and silly generalization that you haven't studied psychology yourself much - if at all. You encounter successful applications of psychology in your daily life regularly without realizing it, and the influence of psychology on other sciences is also significant.
Damn_registrars has no butt-hole. Damn_registrars has no use for a butt-hole.
Sorry, I never worked out the math. I did talk to a physics grad student about the concept (of refactoring the equations to put all of the distortion into time) and he said it was valid. I was never an advanced math student, and tensors baffle me, so I'm not the person to work out the math. I just throw out the idea from time to time to see if someone else will develop it.
But I do think it would work.
I think we've pushed this "anyone can grow up to be president" thing too far.
Systemic
See, what you're missing is simply that it's turtles all the way down.
No it isn't! Didn't you see "The Color of Magic" ? 8-)