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Testing Quantum Behavior — From Earth to the ISS
KentuckyFC writes "Einstein famously believed that the instantaeous effect of quantum entanglement would allow 'spooky action-at-a-distance' in violation of special relativity. Every test of entanglement on Earth has so far agreed with quantum mechanics but naysayers continue to point out various loopholes that might allow the results of these experiments to be determined in advance rather than instantaneously as QM suggests. Today, an international team of scientists is proposing the mother of all entanglement experiments, to be performed in space. The plan is to send entangled photons between an observer on the ground and one on the International Space Station. By the peculiarities of special relativity, the high relative velocity between the observers means that both will always be able to claim to have carried out their measurement first, thereby ruling out the naysayers' arguments (abstract). The experiment, called Space-QUEST, would be housed aboard Europe's Columbus module and would give the much-derided ISS a stab at doing some decent science for a change."
I posted this next week and it's still the first post.
America, Home of the Brave.
Apparently the entangled photon link they were using to host the webpage couldn't hold up under the strain of Slashdot.
Kind of like the chicken and the egg.
TANSTAAFL GIGO Acronyms to live by!
Just that...
Scientist used Entangle!
It's super effective!
Photon capture device go!
You entangled a photon!
It was added to your photondex.
Knowledge is power. Knowledge shared is power lost.
You entangle 2 photons, f.e. by creating them at the same time from the same decay-process.
would give the much-derided ISS a stab at doing some decent science for a change
That won't necessarily help with the derision, as nobody denies the fact that interesting experiments are possible in space. The main point of contention will still be if you need to keep live persons there continuously to perform them. It'd have to be shown that a satellite or a simple orbiting mission couldn't have performed the same experiments for a fraction of the total costs.
Rome taught me patience and assiduous application to detail. Virtues which temper the boldness of great, general views.
Remember that Niels Bohr denied that such a test of nonlocality was possible. Einstein had said that this phenomenon was "incredible" in his "EPR" article, thus rejecting his own prediction. And Bohr replied in effect that such things were taboo metaphysics.
Michael J. Burns
I just thought Space Quest was an amusing and juvenile way to waste time as a teenager.
This will be really neat, but do we need to have people on the space station to do this experiment? It's not like someone going to be observing the photons with his or her eye and agreeing or disagreeing with the an observer on the ground?
--- http://davidnehme.blogspot.com
I hope they remember to save their results often.
As I understand it, a quantum entangled photon is very fragile. I don't understand how or why it's fragile, but wouldn't that make this extraordinarily difficult to do? The trip to the ISS is pretty bumpy.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
they will need to enlist the help of Roger Wilco.
Sure it would be nice to do even more, and sure the costs are high (in part due to the STS, a nice but incredibly inefficient LV), but all this group-thinking about the "white elephant" ISS is akin to saying that kernel programming is easy. It's stupid, flat wrong and insulting for the people that get a lot of good work and science done.
There's a hidden treasure in Python 3.x: __prepare__()
Why not put the experiment on a probe traveling further and further away from earth?
Or perhaps on the moon.
Or mars.
This is actually a fairly exciting bit of science.
-- If you try to fail and succeed, which have you done? - Uli's moose
There's a hidden treasure in Python 3.x: __prepare__()
I'm not sure what you are trying to suggest, but you can't use entangled photons to communicate faster than light.
I've not RTFA - it's down - but basically the EPR effect allows someone to create two photons and then measure if their polarization is H or V. The result is completely random BUT, both photons will always give the same result.
Now Alice measures her photon first and lets say we get H, then Bob's photon must instantaneously turn into H (previously it was a mixture of H and V - the dead and alive cat) so that when he measures his photon he also gets H.
What's already been done is to ensure that Alice and Bob decide what measurement to do, and make the measurement, so close to the same time that it's impossible for there to be any way for Bob's equipment or photon to "know" what Alice is going to do (or vice-versa) except at superluminal velocities.
But because Alice and Bob are in the same inertial frame there's still, at least in theory, a concept of who did the measurement first and who did it second. (Alice and Bob can have synchronized clocks and record the time they did the experiment. Then they can, using normal communication, tell each other what time they did the experiment and they'll both agree who was first and who was second.)
What this experiment will do is mean that Alice and Bob won't agree about who was first and who was second. Alice and Bob's clocks cannot remain synchronized, so that according to Alice, and people sitting next to her, she did the measurement first, but according to Bob, and people sitting next to him, he did the experiment first. And BOTH will be correct because the two measurements are space like rather than time like.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
Please don't break reality. It's where I keep my stuff.
He's suggesting using entanglement to communicate faster than light. I think he's forgetting that once your manipulate the photon, it will no longer be in sync with its pair.
What's already been done is to ensure that Alice and Bob decide what measurement to do, and make the measurement, so close to the same time that it's impossible for there to be any way for Bob's equipment or photon to "know" what Alice is going to do (or vice-versa) except at superluminal velocities.
Just to clarify this paragraph because I've realized it's confusing.
Alice and Bob both randomly decide to measure the H/V polarization or the +/- (45 degree) polarization.
Then they get together and compare results. Where one has measured H/V and the other +/- then they throw the results away because they don't tell them anything useful, but where they've made the same measurement they find they always get the same (or opposite) results.
It's when they make the measurement that neither they, nor their equipment or photon can "know" what the other is doing.
There's also something called Bell's inequality that basically proves that the results of all of Alice and Bob's possible cannot be "known" by the photon ahead of time. (no local hidden variables).
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
You entangle 2 photons, f.e. by creating them at the same time from the same decay-process.
Ah! It comes from the subtle glow of rotting meat, then.
When our name is on the back of your car, we're behind you all the way!
Of what you do not know, you should not speak.
You must be on Hotblack Desiato's black spaceship then.
America, Home of the Brave.
I've never quite understood why this conflicts with GR. It seems like from Alice's perspective, when they both make their measurements, Bob is the superposition of having the same result or the opposite result. It is only after they communicate (restricted by the speed of light) that his results can be compared with hers and his superposition collapses. In other words, there are two measurements done by Alice, one of her photon, one of Bob, and they don't require any faster-than-light communication.
Am I missing something here?
But I think the second part suggests that if you let your photon bounce around randomly, you may be able to know when it's in sync with it's pair thus knowing the phase of the paired photon.
At the other end, once the fixed photon is in phase it moves to the next "bit" in the message and waits for the pair to be in phase again before "transmitting" the next "bit".
Presumably this all takes place in something approaching nanoseconds.
America, Home of the Brave.
By the peculiarities of special relativity, the high relative velocity between the observers means that both will always be able to claim to have carried out their measurement first, thereby ruling out the naysayers' arguments
Of course, by that same logic, naysayers can always claim that each side carried out its measurement last, negating whatever benefit this "feature" supposedly proves.
space-QUEST is probably the best name for a science experiment ever.
What's the value of information that you don't know?
What naysayers? Naysayers of what? And what are their arguments?
The chicken clearly and undisputably came first... in the dictionary.
Invenio via vel creo
Now Alice measures her photon first and lets say we get H, then Bob's photon must instantaneously turn into H (previously it was a mixture of H and V - the dead and alive cat) so that when he measures his photon he also gets H.
What's already been done is to ensure that Alice and Bob decide what measurement to do, and make the measurement, so close to the same time that it's impossible for there to be any way for Bob's equipment or photon to "know" what Alice is going to do (or vice-versa) except at superluminal velocities.
Schrodinger's cat was either alive all along, or dead all along. The only thing that changes is the knowledge of the observer, not the state of the observed. Similarly with the entangled photons. They are both going to be H polarized, or V polarized the entire time. It's just that the observers will not know which until they make the observation. It's not like Alice's photon somehow transmits an "I've been observed as H polarized" message to Bob's photon. These "both alive and dead" and "mixture of H and V" statements are euphemisms for "Unknown".
That is, unless I'm missing something fundamental.
When our name is on the back of your car, we're behind you all the way!
It doesn't (there are other points where GR and QM conflict, but entanglement is not one of them ). Einstein thought it did because he assumed that any such interaction would be deterministic and could hence be used for communication (THAT would break GR ). Essentially Einstein never liked the idea that the universe was based on randomness, hence the famous "god does not throw dice with the universe" quote. As a consequence he repeatedly tried to disprove quantum mechanics by inventing scenarios in which the random nature of QM would conflict with GR. The surprising, and somewhat ironic, outcome of his attempts was however new insights into quantum mechanical interactions that just seem to confirm the random nature of QM.
Also, to be pedantic about it, entanglement doesn't in principle imply that an interaction is quicker than the speed of light. You could alternatively claim that the interaction occurs with the speed of light, but the ENTIRE UNIVERSE ends up in an indeterminate state similar to that of Schrödinger's cat until you receive Alice's message. Thus you can keep interactions restricted to the speed of light ( locality ) but in order to do so you would have to throw out the notion that Alice exist when you do not hear from her ( realism ).
In practice throwing away realism would force you into a rather solipsist interpretation of reality which I think even Kant would have issues trying to accept, and thus most of the time we just stick with the much more comfortable notion of having a reality with instantaneous long distance interactions. If nothing else this is a lot easier to visualize than imagining the entire world entering a superposition of states until you receive Alice's message. From a purely physical point of view the two cases are indistinguishable however, so it doesn't really matter either way.
He famously hated the idea of spooky action at a distance, and never accepted QM. He certainly didn't advocate it.
The both 'alive and dead' IS NOT an euphemism for unkown... A single system can be in a superposition of two states. In this case we are talking about a single system consisting of two photons. Measuring the state in a certain base on one side WILL collapse the wavefuntion of the entangled pare. See for example also the 'wheelers delayed choise experiment': http://en.wikipedia.org/wiki/Wheeler's_delayed_choice_experiment
However, even if the system is 'pushed' into one of the eigenstates of the measurement machine, it can still not be used to transmit information faster then light.
Isn't there a way to tell whether a photon qubit is still coherent or not? That might allow communication. For example, in an experiment where single photons (one at a time) were sent out that could go through either one of two openings, an interference pattern emerged suggesting that the photons actually went through both openings simultaneously (in different parallel universes, possibly). If a detector was added to figure out which opening the photons had taken, the interference pattern disappeared. If you can invent some kind of similar or different experiment that will give a different result for polarized and mixed state photons (for example, if I'm not making some fundamental mistake, the same setup with two openings but each opening equipped with a polarization filter), the ISS can act as the detector. Use a trickle of entangled photons while the ISS is or is not measuring the photons, and check whether an interference pattern comes out. If yes, they just transmitted (or are about to transmit?) a one. Otherwise, it's a zero. Although on second thought, this entire setup will probably count as a measurement for the quantum gods, they can't possibly be that easily fooled :-)
By the way, I don't know anything about quantum mechanics other than what I picked up here and there...
Classical physics tells us that if you know the angle of polarization of a photon, then its chance of passing through a polarizer is the square of the cosine of the difference in angles between the photon and the polarizer. If you have a 45 degree photon, it will always pass a 45 degree polarizer, have a 50% chance of passing a 90 degree polarizer, and will never pass a 135 degree polarizer.
QM tells us that when you have two entangled photons and measure both of their polarizations, the chance the results will correlate is the square of the cosine of the difference in angles between the two polarizers . If you measure them at the same angle, the results always correlate. If you measure them at 45 degrees apart, the measurements correlate 50% of the time. If you measure them 90 degrees apart, the measurements never correlate (the results are always opposite). No matter how you look at it, this means either the results are predetermined at the time the photons are created based on the angles the polarizers will be at the time the measurements are taken, or that one measurement somehow influences the other later so the past isn't immutable.
Either way you look at it, it means the universe doesn't work the way we expect it to. If you're a glass-half-full person you want to believe in FTL and time travel, and if you're a glass-half-empty person then you think maybe the universe is deterministic.
That's why this stuff gets everyone who understands its implications all in a tizzy.
Fun with Anagarams! LADS HOST, SHALT DOS. HAS DOLTS. AD SLOTHS, HATS SOLD. ASS HO, LTD.
Could you please explain what a measurement is, since clearly interaction with something isn't enough or it would be measured by the air.
thank God the internet isn't a human right.
they actually are both H and V polarized at the same time. you can think of them as just being "unknown" for the sake understanding why you cant use it to communicate faster than light, but it isnt what's actually going on.
we know this because in a quantum superposition, different possibilities in the superposition can interfere with other possibilities, making certain results more or less likely. this is shown by the double-slit experiment. shooting photons at a screen through two slits produced not two stripes like you'd expect, but several stripes. this is because each photon went through 2 waves of possibilities, one through each slit, and the waves then collided with each other, making certain ares of the screen more likely to be hit than others.
That is, unless I'm missing something fundamental.
Your description of entanglement is known as a "hidden variable theory" of QM, and exactly what this experiment is trying to refute once and for all. QM really imply that the cat is both alive and dead.
Higher Logics: where programming meets science.
You have missed something fundamental.
Here is the issue:
If you assume, as you do, that the photon has some predetermined phase A (for angle), then the likelihood of it passing through a filter at another angle B is cos(A-B) * cos(A-B). Experiments testing this by passing photons through a filter at angle A (all photons that make it through have phase A) and measuring how many make it through a filter at angle B confirm it.
BUT, if the photon had an initial angle A, and Alice and Bob both have filters at the same angle B, EVERY TIME the photon with either pass through BOTH Alice and Bob's filter, or NEITHER Alice nor Bob's filter. That can't be explained by your classical model. It can only be explained by "spooky action at a distance".
(It can also be explained by assuming that the universe splits into two cases, one where the photon passes through both filters, and one where it passes through neither, and some mechanism that prevents communication between the universes. This is the many-worlds or relative-state formulation of quantum mechanics, discovered by Hugh Everett in 1957 but unpopular until many years later.)
IHA14YOBSIPBIANAP.
(I have a 14 year old BS in Physics, but I am not a physicist).
That is, unless I'm missing something fundamental.
Yes, you're missing something fundamental.
Going back to one photon.
We'll have four polarization states H, V (the normal horizontal and vertical polarization) and +, - the 45 degree polarizations.
Now Alice produces a stream of H photons and sends them to Bob. Now if Bob measures to see if they're H/V then he will always get H.
But if Bob measures if they're +/- he'll get 50/50 + and -, with each individual photon being + or - at random.
After measuring +/-, if Bob then remeasures H/V he'll again get 50/50 H and V. The measuring of +/- destroys the knowledge about H/V
If Bob measures at an angle other than 45 degrees then he'll get different proportions but he'll get sin^2 theta with one polarization and cos^2 theta with the other polarization.
Now lets consider entangled photons that will always give the same result for Alice and Bob. Initially we'll assume that Alice will always measure the horizontal polarization (0 degrees) Now lets consider that the photon "knows in advance" whether it will go through a horizontal polarizer i.e. it has (an infinite number) of hidden variables. Regardless of what measurement Bob does, an ensemble of photons can distribute values amongst these hidden variables so that Bob gets the expected correlations relative to Alice and the angle of his measurement.
But now let Alice vary her angle as well. Now the correlation depends on the difference in angle between Alice and Bob. But that angle isn't known (and hasn't even been decided) at the point the photon has been created. It could have a big "look up table" saying "If Alice angle is n and Bob angle is m then do/don't go through Alice's filter and do/don't go through Bob's filter BUT the photon that arrives at Bob's detector has to know what measurement Alice will/has done and the photon that arrives at Alice's detector has to know what measurement Bob will/has done.
But because Alice and Bob independently randomly decide what angle to measure "long" after the photon was created and their independent decisions are made so close together in time that neither can know what the other has/will do when they make their measurement due to the speed of light limit then there is no way for the photon to use its "lookup table" and get the correct statistical results.
It doesn't matter how you construct that "lookup table", unless you allow some sort of faster than light communication, using the lookup table will give different results to QM.
If you want the formal maths for that bit of hand waving then lookup Bell's inequality. He actually deduced the inequality that could be tested to prove no local hidden variable theorem was consistent with the results of QM based on measuring particle spins while most of the tests that have been done have used polarization of photons but the underlying theory is the same.
These experiments have already been done, and Bell's inequality has come down on the side of QM. Because Alice and Bob make their measurements so close together in time, not all observers will agree which one is first but (perhaps unfortunately) Alice and Bob will agree who was first and who was second. What this experiment does is close even that loophole - even Alice and Bob will be unable to agree who made the first measurement and who made the second.
Tim
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
My first program:
Hell Segmentation fault
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
How on earth do you transport these photons to two separate locations without their container affecting them?
The observer in the Schrodinger's Cat 'paradox' is the first particle to come in contact with the cat (typically a photon). If you define the entangled quantum state as the cat plus the apparatus then it's typically an Infrared photon passing through the air inside the box, and if you define the entangled state as the whole box, then it's typically a photon in the room. The 'observer' could be an electron orbiting one atom in the table top supporting the box, or various other possibilities. That's what QM means by observation, not a living entity, or a self aware entity with memory, or a self aware entity with memory actually trained in Quantum Physics. The first particle outside whatever you've already defined as an un-collapsed state vector, that interacts with it, reifies the state vector. An un-reified state vector with the mass of a cat 'collapses' in an extremely tiny fraction of a second.
The only known way to prolong this is by extremely low temperature methods, where something with the mass of a cat could theoretically be a Bose-Einstein condensate and not one of the three classical states of matter.
Who is John Cabal?
How exactly did you manage to lump Iran, China and the EU together?
Realise I've not really answered this.
Bob can't be in a superposition of the two results because Alice's measurement has already determined what result he must have got. If Alice sends a polarized photon (that she's created and knows the polarization) to Bob then she knows what result Bob will get if he measures the same polarization even if Bob doesn't know what measurement to make and just makes a random guess.
The speed of light prohibits Alice from knowing whether Bob actually bothered to do the experiment until later but Alice knows in advance, provided Bob hadn't taken a coffee break, what result Bob got, even though, from Bob's POV, his result was completely random.
i.e. Alice and Bob can have a random number generator that can simultaneously generate the same stream of random numbers at opposite ends of the universe and yet nobody can predict what the next random number will be until Alice and Bob makes their measurement.
(Of course, in the simple random number example, the results could be explained by a local hidden variable but we can design experiments where a local hidden variable cannot explain the results)
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
So this does allow faster than light communication, right? If Bob modulates his angle, Alice will be able to tell.
No.
They can't communicate using this.
Alice can't tell if Bob modulates his angle. Alice and Bob can't even agree who made the measurement first which makes it kind of hard to imagine how they can use it to communicate.
Alice measures her photon and gets one of two results completely at random.
Bob measures his photon and gets one of two results completely at random.
When they get together they discover that, although their individual result were random, their combined results display a correlation related to the relative angle of the polarizations they measured.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
You let them go there on their own. Photons have this innate ability to go places at the speed of light without having to put them in a box and carry them there.
Yes, there is a problem with them interacting with the environment and decohering but that's an engineering problem rather than a physics problem. Provided you're not sending them too far then most will get through without issue.
In any formal experiment you have to allow for the probability of decohering - and so you don't expect 100% correlation. The trick is to get that probability low enough that the errors don't swamp the signal.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
QM conflicts with GR in the same way that for example scan-converting a line segment produces a solid line when you step back, but produces "ladders" and "jaggies" at a pixel scale. You can generalize about formulas for lines, but that is not going to explain the value of a particular pixel.
But more to the point, entanglement is like a pointer. If you have "p = q = &val" and send p to the space station and q on earth and measure *p and *q there are no superposition of states or multiple universes or faster than light travel. There is only the dereference.
Ok sure the 'universe is a simulation' may not be predictive, but as a mental framework maybe it helps to make sense of QM. Like particles being miniature solar systems did until we learned more.
I can't wait until they perform the Leather Goddesses experiment on Phobos.
That might allow communication.
Never!
Faster than light communication violates causality - A causes B but B happens before A. It's just absurd.
If you think you've found a way around the speed of light limit then there's something you don't understand yet.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
And there's the rub, and the reason why people are still trying to prove QM after a hundred years. The equations appear to indicate that one of the following MUST BE FALSE:
1. Quantum Mechanics.
2. Locality.
3. Realism.
All the experiments performed so far strongly support QM, so we can't dismiss that. If locality is false then we have Einstein's spooky action at a distance and a conflict with GR. If realism is false...then nobody knows where the hell we are, or what we are.
But one of them *has* to be wrong. All these experiments are trying to prove is which one.
Genocide Man -- Life is funny. Death is funnier. Mass murder can be hilarious.
What I found fascinating was seeing this demonstrated to the naked eye using polarized lenses.
When two polarized lenses are placed next to each other at 90 degree angles, no light gets through, because all wavelengths are being blocked.
However, putting a third polarized lens between them at 45 degrees to both makes the group transparent again-- like looking through shaded glass, some of the light was blocked, but not all.
Completely counter-intuitive. I'd have had a hard time believing it without playing with the lenses myself.
It sounds like we are on the road to inventing the Ansible (Authoress Le Guin's term), allowing instantaneous communication, which would come in very handy in driving rovers around on Mars, for example.
They hate us the most right now.
3-4 months, last I checked. Quite a hunk of change if you ask me.
This Disney-esque version of history is forced into an oversimplified mentality, to the point of being nonsense. It's not like Einstein was some old, irrational curmudgeon, where QM was concerned.
Einstein disagreed with QM early on, when it was still in it's infancy. He did not really try to disprove it, per se, so much as he just repeatedly extrapolated, based on the known data, different QM scenarios that seemed to apparently conflict with GR. This led to research and improvements to the theory of QM, to the point that Einstein was eventually satisfied. So much so that trying to unify GR and QM took up the last several years of his life.
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
Roger Wilco on that one ISS. I just hope you keep things clean whilst doing the experiment.
And wow, "neater" is indeed the captcha code this time.
I suppose you're right. I was actually going to say you were wrong, but came to my senses while I was writing why :-)
In itself, communicating with someone in the past would not have to violate causality as long as this person could not affect *your* past. If you send a message to someone now, he received it last week (many light years away), sent back the reply last week, and you receive it now (shortly after you sent the original message), causality is not affected. Even better, if you start moving towards or away from him at a sufficiently high speed, he will suddenly be in the future anyway. Big deal, so I thought.
But then I figured it would be trivial to set up more than one connection, with different time differences, send a question with one link and have the reply sent via another link...
So yes, you are right :-)
When they get together they discover that, although their individual result were random, their combined results display a correlation related to the relative angle of the polarizations they measured.
Of course. The entangled photons are images of each other. If I measure one, the other is going to have a related value. So it doesn't matter who measures what first, or if one measures and the other doesn't. Once one is known, the other is known.
When our name is on the back of your car, we're behind you all the way!
For all the naysayers of ISS science, here is the list of past and present experiments for your review:
ISS Experiments by Expedition
Please note the count of experiments currently stands at 561, and the focus ranges from virology, to fluid mechanics, to relativity, to astronomy, and even engineering validation (not simply of space station components, but also of fully independent technologies). That's nothing to sneeze at.
And while a fairly large portion of them are relatively minor or PR projects like sleep habits in 0g and the Buzz Lightyear "teaching from space" program, there is an ample number of experiments designed specifically to take advantage of the unique environment the ISS offers and with a variety of potential future applications.
And don't forget the majority of these so far were conducted prior to the installation of the two primary laboratory modules on the ISS: Columbia, launched late last year, and Kibo, which is 2/3 delivered as of last week. These have also been done mainly by 2 or 3 man crews, with occassional help from shuttle crews. Once the ISS switches to a 6 man crew rotation, the rate at which science work is completed will be greatly enhanced.
But of course, carefully planned, executed, and generally useful science isn't as fun to talk about as broken toilets, so we'll just continue ignoring the successes of the ISS and focus only about the cost overruns, deleted components, and occassional operating problems.
I'm pretty sure that the cat in the box thing is usually taken the wrong way. It was probably meant to show something was wrong with the interpretation rather than to suggest the cat was somehow both alive and dead. Cats are not both alive and dead.
The particulars of quantum non-locality don't conflict with relativity, which doesn't strictly require locality, but merely causality. Causality and locality are generally conflated because having locality gives you causality. But, certain ways of breaking locality don't screw up causality, and quantum non-locality is one of them. You can't transmit any information non-locally using quantum effects, in essence.
SIGSEGV caught, terminating
wait... not that kind of sig.
Cats are not both alive and dead.
Exactly. But QM says they are.
H polarized photon = Cat dead. V polarized photon = Cat alive. 45 degree polarized photon = Cat dead, 135 degree polarized photon = Cat alive.
Until Alice and Bob make their measurements we really do find that the cat is both dead and alive.
But what does "measurement" mean? If we really were using dead/alive cats to do this experiment (currently we lack the ability to keep something the size of a cat in a superposition of states) then presumably the cat knows if it's alive. But where/how does this stop. If not a cat, what about a mouse? An amoeba? A virus? A protein? an O2 molecule? An atom? An electron?
I think currently we're up to the atom or small molecule point with still no sign of QM breaking down.
There are ways around these conceptual problems, many worlds being one.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
Fun with Anagarams! LADS HOST, SHALT DOS. HAS DOLTS. AD SLOTHS, HATS SOLD. ASS HO, LTD.
One of the major problems encountered in time travel is not that of accidentally becoming your own father or mother. There is no problem involved in becoming your own father or mother that a broad-minded and well-adjusted family can't cope with...
The major problem is quite simply one of grammar, and the main work to consult in this matter is Dr. Dan Streetmentioner's Time Traveler's Handbook of 1001 Tense Formations. It will tell you, for instance, how to describe something that was about to happen to you in the past before you avoided it by time-jumping forward two days in order to avoid it. The event will be described differently according to whether you are talking about it from the standpoint of your own natural time, from a time in the further future, or a time in the further past and is further complicated by the possibility of conducting conversations while you are actually traveling from one time to another with the intention of becoming your own mother or father.
Most readers get as far as the Future Semiconditionally Modified Subinverted Plagal Past Subjunctive Intentional before giving up; and in fact in later editions of the book all the pages beyond this point have been left blank to save on printing costs. The Hitchhiker's Guide to the Galaxy skips lightly over this tangle of academic abstraction, pausing only to note that the term "Future Perfect" has been abandoned since it was discovered not to be.
i wish i could stop
Oh sorry, didn't see your subject line. I thought you were refering to the overall cost of the ISS. Sure, $2 billion is something like a couple days of Iraq. But you got to remember that on $2 billion a year, I bet we could stick up and maintain a few Bigelow inflatables. Wouldn't need the Shuttle or another heavy lifter like the Ares V either.
Double-slit-type interference has been observed with buckyball, and some biological molecule that is larger or on the same scale as buckyball, but the name of this molecule escapes me at the moment...
Bah, relativity is for macroscopic objects and quantum mechanics is for tiny quantum-scale objects.
Just like spiders can lift 10 times their weight, but humans can't. Different scales mean different rules.
Well that depends on whether you're talking about GDH (gross domestic hatred) or GDH per capita. Per capita, countries you've been at war with more recently probably hate you more, but I guess even if China can muster a small amount of hate per person, that's gonna add up quite a bit more than other countries, even where people have to wake up extra early in the morning just to get all the hating in.
The revolution will not be televised... but it will have a page on Wikipedia
No, "hidden variables" refers to information being carried with that which is observed, the particle. That's why they say "local variable". What I am referring to is particles in physically different locations having shared state (ie, the variable referenced exists outside of normal space and time, ie it can be thought of as a function of a simulation). Or, in other words "spooky action at a distance".
In pretty much every case imaginable the programming model corresponds to quantum mechanics, including pointers. Yeah, it's not predictive so it doesn't help answer the questions about the universe, but it can help to ask the right questions.
It ISN'T useful for FTL communication.
FTL communication is IMPOSSIBLE. It VIOLATES CAUSALITY.
What that means, in plain English, is that A can cause B but B can happen before A.
This is hard to grasp because we believe in a universal time and a preferred reference frame. But however intuitive that might be we've got to let go and accept the fact that we can have two events where it's impossible to decide which happened first and which happened second.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
Physicists aren't overlooking this at all.
This is called a local hidden variable theory.
Back in the 1960's (1969 IIRC) Bell proved that it doesn't matter how you design your hidden variable theory, there are experiments that will give different results from what QM predicts.
The most famous of these experiments was done by Aspect in 1982. He found that the results were compatible with QM and incompatible with ANY local hidden variable theory.
Ever since then people have been trying to come up with theories that can explain the EPR effect. Causality going backwards in time, many worlds, but, to date, nobody has come up with any (even theoretical) experiment that can give us any handle on what might really be happening "under the hood".
And a few people have been looking for loopholes in the various experiments that would mean that a hidden variable theory could still be true.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
It is great that spooky action at a distance is finally making it into the mainstream. You might consider updating your topic sentence though. Spooky action at a distance is what Einstein steadfastly refused to believe in. Einstein, Rosen & Podolsky's disbelief inspired them to published a paper about the incompleteness of quantum theory (I didn't do it - it was the hidden variables). Cheers
How can China hate us? They want to be us!
Oops, sorry, I just answered my own question.