Human Eye Could Detect Spooky Action At a Distance 255
KentuckyFC writes "The human eye is a good photon detector--it's sensitive enough to spot photons in handfuls. So what if you swapped a standard photon detector with a human eye in the ongoing experiments to measure spooky-action-at-a-distance? (That's the ability of entangled photons to influence each other, no matter how far apart they might be.) A team of physicists in Switzerland have worked out the details and say that in principle there is no reason why human eyes couldn't do this kind of experiment. That would be cool because it would ensure that the two human observers involved in the test would become entangled, albeit for a short period time. The team, led by Nic Gisin, a world leader on entanglement, says it is actively pursuing this goal (abstract) so we could have the first humans to experience entanglement within months."
Re:not quite a first, guys (Score:5, Insightful)
We live in the physical world and experience entanglement all the time
Absolutely. This is just a PR stunt, and very bad science if you think that science involves not misleading naive people for the purposes of PR.
The claim that the two human observers would be entangled is problematic at best. Not only wouldn't any entanglement last longer than the coherence time of a human being (~10^27 particles in thermal equilibrium at 310 K!), it is difficult to understand how the researchers would fail to notice that in some reference frames one observer would detect their photons quite a bit sooner than the other observer. In those frames the entanglement of the observation systems never happens, which is why sensible people don't talk about such things.
The very notion of assigning "an instant" to an "event" that is by its nature nonlocal is simply incoherent. This is what makes the whole business spooky: it cannot be described using the relativistic physics that necessarily describes the world of human experience.
Re:Frogs (Score:3, Insightful)
I've heard that frogs have the ability to detect single photons [iop.org]. This is from a cryptographer who jokingly proposed a frog-based system for quantum key distribution. But on a more serious note, what does it really mean for two people to become entangled? And does it matter that the photons are detected by a human retina? Could the entanglement just as easily happen if the photons were fired into my left butt-cheek?
Furthermore, how does one "record" it such that the data can be retrieved? Yes, I know your dumb girlfriend "saw" the flash, and can report it, but it's still subjective. It's not like saying "hmm, that photon bumped the meter to 3.2eV"
Re:Frogs (Score:5, Insightful)
I think perhaps we are constantly entangled, but that our "consciousness"
Just because it's unusual to us doesn't mean it's mystical or magical. For your idea to actually be science and not philosophy you'd need a much better grasp of what you're actually saying. Saying something like "we're all constantly entangled" doesn't really mean a lot, since entanglement doesn't occur on a macro-scale.
People have tried to tie together mysticism, quantum mechanics, and consciousness before. At best it's an interesting exercise in thinking. At worst it's nonsense gibberish. To my knowledge it's never really produced anything approaching science.
Are they for real? Its not April 1st yet... (Score:5, Insightful)
Re:Not quite... (Score:4, Insightful)
Observers would not become entangled (Score:2, Insightful)
> the two human observers involved in the test would become entangled...
Not really. By definition, once "observed" the photons cease to be entangled (the wavefunction collapses)- and by "observed" we mean that one or the other photon is sensed by a rod or cone in one of the observers' eyes.
Re:Not quite... (Score:3, Insightful)
Except that according to quantum mechanics, if after handing out the envelopes, you hypnotize Alice to see heads when she opens the envelope, Bob will see tails.
Yes, that's a dreadful oversimplification but that's the analogy you gave me to work with.
Your scenario is an accurate analogy for the hidden variables hypothesis (and local realism). However, experimental evidence doesn't support hidden variables and local realism. That is, that the measurements are of some characteristic that is located entirely within what is measured such as half of a coin.
The interesting part is that QM shows that spooky action at a distance does exist but cannot be used to convey information faster than light.
As for what is meant by the paper, it's just an interesting way to get the instrumentation out of the way and see the effect directly. That is, it's just kinda cool.
Re:Not quite... (Score:4, Insightful)
Now Alice opens her envelope and sees tails. So she knows Bob must have heads. (...) Alice only has access to the information she *brought* with her when they separated.
That's correct, but that's not the whole story. From what you said, it looks like classic mechanics is good enough to explain it, and it's not.
The problem is that there is not only one way you can measure the state of this "coin" -- depending on the orientation of your measurement, you get heads or tails on that specific orientation. So, when Alice measures the coin in a specific orientation, this *orientation* is "felt" by Bob's coin, and it may influence the result of Bob's measurement. That effect simply can't be explained by classic mechanics.
For a more detailed explanation, see the section on Bell's Inequality in http://www.eecs.berkeley.edu/~vazirani/f04quantum/notes/lecture1.pdf [berkeley.edu] (warning: requires a bit of math).