Testing Quantum Behavior — From Earth to the ISS 196
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."
Spooky (Score:5, Informative)
Science coverage on /. is crappy (Score:5, Informative)
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.
Re:Could it be useful? (Score:5, Informative)
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.
Re:Derision (Score:4, Informative)
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.
I think it's like a zoo. Maybe the animals inside are being held in some sort of unfair captivity (I tend to think that in modern zoos most animals are pretty satisfied, but let's not go into that), but the interest and money generated by those animals creates the world's largest resource for saving their wild relatives.
Even if the ISS is never used in a way that provides more direct scientific knowledge per euro than unmanned missions, I believe it's worth it in the long term.
Re:Could it be useful? (Score:3, Informative)
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.
Re:Science coverage on /. is crappy (Score:5, Informative)
Re:Could it be useful? (Score:1, Informative)
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).
Re:Could it be useful? (Score:5, Informative)
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
Re:Science coverage on /. is crappy (Score:5, Informative)
1, Fox News actually went to court and won an advance judgment that said, even if it could be shown that the newscasters had deliberately lied about a concealed source being reasonably unbiased, and it was proved that the source actually worked for a political party and was paid to make the claims that it made, Fox would still be protected by the normal laws about concealing the identity of sources and this situation wouldn't constitute possible malice with respect to libel laws. Name another news agency that has even sought such a protection.
2. In 2002, there was a study of the media where the only thing that was examined was accuracy of attribution. That is, if a news source quoted a person and said that person was a lawyer in the state of New Jersey, the study checked to see if the person was really liscenced before the New Jersey Bar at the time. If they said a source was a Vice President at a fortune 500 company, the study checked to see two things - was that company really in the 500, and was the guy's title really VP and not Assistant VP or similar. NPR and BBC both scored in the 3.8 to 4 out of a possible 5 range. PRI, MSNBC and ABC ran somewhere near the middle. Where did Fox score? 2.2 - right next to Al-Jazera!
Re:Science coverage on /. is crappy (Score:5, Informative)
Re:Science coverage on /. is crappy (Score:3, Informative)
Re:Science coverage on /. is crappy (Score:3, Informative)
Re:Could it be useful? (Score:4, Informative)
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.
Re:Science coverage on /. is crappy (Score:3, Informative)
Note that Fox did not deny they were falsifying the news story on BGH; they argued only that what they did was not covered by the "adopted rule" of the FCC. A purely technical legal argument to defend broadcasting information they intentionally distorted and knew was wrong.
And that is a new organization?
http://www.foxbghsuit.com/ [foxbghsuit.com]
http://www.2dca.org/opinion/February%2014,%202003/2D01-529.pdf [2dca.org]
Re:Robust enough? (Score:3, Informative)
Re:Science coverage on /. is crappy (Score:5, Informative)
The parent post is overrated. It's not entirely correct and it's not very coherent.
That is before any of the hardware had been launched. But it's unsurprising that the OP could be dissatisfied with the experience. Aside from being a government program and all the cliches that entails, the ISS has gone through many redesigns, and the effort of cooperating internationally has been an added source of delay and cost. He's not alone in such criticisms and the ponderous nature of government programs is one of NASA's biggest problems.
The shuttle is a much more expensive spacecraft to operate than the ATV. The shuttle's advantages are it's manned, it is a versatile work platform, and it can carry cargo back to earth. It's overkill for basic resupply. Although Jules Verne didn't because there was a large amount of pressurized cargo on board, the ATV can carry up to 4.7 tonnes of spare propellant...much more than either the shuttle or Progress. There may also be a commercial option available for re-supply and reboost in the next 3-4 years through the COTS program.
There is absolutely nothing wrong with Soyuz or Orion performing crew rotation. Both of these craft have lower operating costs than the shuttle, and lower projected loss of crew probability.
Total BS. The international partners are well aware of how much reboost the ISS needs and are planning accordingly. There is no secret. Progress, ATV, or the shuttle alone can't do all of the reboost, but combined they can. Also, once construction is finished, the ISS will be boosted to a slightly higher orbit to reduce the effect of drag. Lastly, the ISS is at nearly maximum drag, with only one more solar array to be added, but still growing in mass. Added mass works out net neutral. The momentum reduces the effect of drag just as well as it reduces the effectiveness of reboosts.
This statement, at least, is based mostly in fact. ISS is somewhat contentious at NASA, but it has its supporters and detractors. There will be quite a few glad not to have to divert resources to it, and plenty others frustrated by the loss of a unique laboratory environment and work platform. I doubt hardly anyone there would argue that it's completely without value, but many feel the money would be better spent elsewhere.
The contention of crooked accounting is unsubstantiated. If there's crooked accounting it goes on at lower levels, but the OP has provided no evidence of it. NASA funds are accounted for at the higher levels in the annual budget allocations. The problem with accounting for exact costs is that ISS draws on programs that have their own independent budgets. How much of the cost of the shuttle return-to-flight program should count towards the ISS, for example? More on cost here. [wikipedia.org]
Scaling (Score:1, Informative)
Just like spiders can lift 10 times their weight, but humans can't. Different scales mean different rules.
Re:Science coverage on /. is crappy (Score:1, Informative)
Behind TV Analysts, Pentagon's Hidden Hand [nytimes.com]