Quantum entanglement shows that reality can't be local • Hacker News Board

Re: Quantum entanglement shows that reality can't be local

#51

Post by mrose » Tue, Oct 30, 2012, 7:32 PM UTC

cs702 wrote: post #44

I've always found classical Newtonian physics, the Special Theory of Relativity, and (to a lesser extent) the General Theory of Relativity to be understandable at an intuitive level, but quantum phenomena just baffles me, even when I think I "understand" it. PS. IvoDankolov: I find it difficult or impossible to think intuitively about quantum phenomena.

This Heisenberg quote puts the general "feeling" of quantum physics into an understandable form: “What we observe is not nature itself, but nature exposed to our method of questioning.”

Re: Quantum entanglement shows that reality can't be local

#52

Post by IvoDankolov » Tue, Oct 30, 2012, 7:33 PM UTC

cs702 wrote: post #44

I've always found classical Newtonian physics, the Special Theory of Relativity, and (to a lesser extent) the General Theory of Relativity to be understandable at an intuitive level, but quantum phenomena just baffles me, even when I think I "understand" it. PS. IvoDankolov: I find it difficult or impossible to think intuitively about quantum phenomena.

In what terms do you think you "understand" it?

What do you make of this problem with distant entangled particles? The double slit experiment and interference in general? The Heisenberg uncertainty principle? (Or as I'd like to call it, Heisenberg's horribly mislabeled-in-order-to-confuse-students principle)

A shot in the dark - many of the problems with coming to terms with quantum mechanics arise from trying to impose on it that it should somehow behave like classical mechanics, or that somehow we humans stand above it and look down upon it, and heaven forbid that we're part of a qunatum system).

Re: Quantum entanglement shows that reality can't be local

#53

Post by DanBC » Tue, Oct 30, 2012, 7:34 PM UTC

ChuckMcM wrote: post #3

This is for me the most interesting part of the whole teleportation / entanglement research. When these papers started coming out we debated the notion of 'faster than light' communication. The counter argument was that you had to move the particles apart and that was constrained by the speed of light. Then the question of "when" the state was resolved was pondered. There were two thought experiments proposed at this…

Greg Egan - I can't say more because spoilers.

Re: Quantum entanglement shows that reality can't be local

#54

Post by kinghajj » Tue, Oct 30, 2012, 7:35 PM UTC

MBlume wrote: post #27

nessus42 wrote: post #23

This article completely ignored the Many Worlds Interpretation, which preserves all of realism, locality, and Relativity.

Yeah. It shouldn't be that surprising that when you arbitrarily assume that part of the wavefunction magically disappears sometimes, you get weird results like non-locality.

The Bohm interpretation has a universal wavefunction and non-locality, though.

Re: Quantum entanglement shows that reality can't be local

#55

Post by tomjen3 » Tue, Oct 30, 2012, 7:36 PM UTC

chiph wrote: post #6

Not a physicist (theoretical or otherwise), but to me the introduction of the concept of "hidden variables" reminds me of the addition of Phlogiston to the body of knowledge. Unless... they're using it as a placeholder for as-yet undiscovered ways that entangled particles can interact, and it's known that it's a placeholder.

Hm I don't think the issue with Phlogiston was that we didn't know what it was, but that rather than try to use the scientific method to make predictions about it, they just wrote down "when a, do b, Phlogiston does x".

In this case they are doing experiments where they expect the hidden variables to do a very specific job (transmit information) and are trying to test whether they do what they expect them to do or not.

That is science.

Re: Quantum entanglement shows that reality can't be local

#56

Post by jrl » Tue, Oct 30, 2012, 7:37 PM UTC

ChuckMcM wrote: post #3

This is for me the most interesting part of the whole teleportation / entanglement research. When these papers started coming out we debated the notion of 'faster than light' communication. The counter argument was that you had to move the particles apart and that was constrained by the speed of light. Then the question of "when" the state was resolved was pondered. There were two thought experiments proposed at this…

That sounds like a very cool science fiction idea :-)

Re: Quantum entanglement shows that reality can't be local

#57

Post by elteto » Tue, Oct 30, 2012, 7:37 PM UTC

cs702 wrote: post #44

I've always found classical Newtonian physics, the Special Theory of Relativity, and (to a lesser extent) the General Theory of Relativity to be understandable at an intuitive level, but quantum phenomena just baffles me, even when I think I "understand" it. PS. IvoDankolov: I find it difficult or impossible to think intuitively about quantum phenomena.

Don't hit yourself too hard, even Feynman said once: "I think I can safely say that nobody understands quantum mechanics."

Re: Quantum entanglement shows that reality can't be local

#58

Post by xanmas » Tue, Oct 30, 2012, 7:41 PM UTC

Liron wrote: post #34

I hate this article, because locality is an important property that we think reality does have. It's like saying "Gravity violates conservation of energy!!!" No it doesn't; quit playing fast and loose with well-understood principles.

Locality in this sense refers to the presence of "hidden variables" as first put forth by bohm and later suggested by other people. It was believed that the various CHSH, HOM, and other bell-inequality inspired experiments would have put a nail in the coffin but critics always came back and say "but you didn't control for X." This experiment is just another in the long line of experiments started by Aspect and continued by others to put bounds on this.

Re: Quantum entanglement shows that reality can't be local

#59

Post by CamperBob2 » Tue, Oct 30, 2012, 7:44 PM UTC

MBlume wrote: post #30

nessus42 wrote: post #25

Earlier quoted context omitted.

Relativity says that you can't construct a rigid beam 25 million miles long.

I think that's going a little too far. If you can construct a "rigid beam" five feet long, I see no way that relativity countermands a "rigid beam" 25 million miles long. It's just that "rigid" doesn't mean what grandparent thinks it means -- info still travels through the beam via pressure waves.

The pressure waves are ultimately manifestations of the exclusion principle, expressed through forces that are constrained to travel at or below c.

So yes, relativity dictates that you can't create a rigid beam 25 molecules long, much less 25 million miles long. There can be no such thing as a perfectly rigid beam of any length.

Re: Quantum entanglement shows that reality can't be local

#60

Post by jlgreco » Tue, Oct 30, 2012, 7:44 PM UTC

ars wrote: post #49

MBlume wrote: post #30

Earlier quoted context omitted.

I think that's going a little too far. If you can construct a "rigid beam" five feet long, I see no way that relativity countermands a "rigid beam" 25 million miles long. It's just that "rigid" doesn't mean what grandparent thinks it means -- info still travels through the beam via pressure waves.

> If you can construct a "rigid beam" five feet long Except you can't. A existence of sound traveling through the beam proves without a doubt that the beam is not rigid.

Exactly, you can only construct beams at any scale that seem rigid at some scale. A 2 foot long piece of re-bar looks pretty rigid, until you look closer.