Nick Herbert's Proof: Quantum Non-Locality Explained

[harrylin]

Herbert's proof is a proof of Bell's theorem by consideration of a two-party, two-setting, two-outcome experiment. In other words, a CHSH-style experiment.

At first sight yes, but I found that details matter as much as they matter with magic tricks (that's one of my hobbies).

[...] I suppose someone who did Herbert's *experiment* wouldn't demand exactly zero error rate in the (0,0) configuration. They'd allow a small error rate. So in effect, test CHSH. CHSH looks at four orrelations. Fix one at +1, and you reduce it to Bell's inequality, which is essentially Herbert.

See arXiv:1207.5103 by RD Gill (me), I uploaded a revised version last night. It will be available from at Tue, 20 Aug 2013 00:00:00 GMT.

I'll have a look at that, thanks!

 

[gill1109]

You're asking for a CHSH style experiment where first one of the four pairs of angles is used for many runs, then a second pair, then a third, then a fourth. First (1,1), then (1,2), then (2,1), finally (2,2). And you want perfect correlation in the first batch of runs.

In a real experiment counting coincidences of detector clicks you'll never see *perfect* correlation if the number of runs is large. You might see near to perfect correlation. What will you do then? Publish a failed experiment?

 

[harrylin]

You're asking for a CHSH style experiment where first one of the four pairs of angles is used for many runs, then a second pair, then a third, then a fourth. First (1,1), then (1,2), then (2,1), finally (2,2). And you want perfect correlation in the first batch of runs.

In a real experiment counting coincidences of detector clicks you'll never see *perfect* correlation if the number of runs is large. You might see near to perfect correlation. What will you do then? Publish a failed experiment?

A set-up isn't an outcome of course, and a near to perfect correlation sounds good to me. However, publication bias as you suggest appears to be a serious problem nowadays... it's a serious risk also with Bell tests. Imagine that Michelson had not published his "failed" experiment!

 

[gill1109]

Yes, magic tricks! Every disproof of Bell's theorem whether theoretical or by computer simulation is based on a conjuring trick. Combination of sleight of hand, the gift of the gab. That's why the QRC (quantum Randi challenge) was invented.

 

[harrylin]

Yes, magic tricks! Every disproof of Bell's theorem whether theoretical or by computer simulation is based on a conjuring trick. Combination of sleight of hand, the gift of the gab. That's why the QRC (quantum Randi challenge) was invented.

Nick Herbert's experiment remains impressive to me, especially at high efficiency; it's perhaps stronger than CHSH. Some imagined loopholes are just nonsense that could distract the audience and even the experimenters themselves. Ever heard of the fakir who throws up a rope in the sky and disappears in the clouds? Apparently such things have been done, but as always, the real protocol was not exactly like that! I'm a bigger skeptic than Randi.

 

[gill1109]

Herbert has a proof, not an experiment.

The experiment corresponding to Herbert's proof would be a CHSH experiment with special choice of settings, applied in a special sequence (known in advance), and a more stringent criterium than "violate CHSH inequality". Herbert requires "violate CHSH inequality and get perfect correlation with the first of the four setting pairs".

So it is stronger in just once sense, but weaker in others.

 

[harrylin]

Herbert has a proof, not an experiment.

The experiment corresponding to Herbert's proof would be a CHSH experiment with special choice of settings, applied in a special sequence (known in advance), and a more stringent criterium than "violate CHSH inequality". Herbert requires "violate CHSH inequality and get perfect correlation with the first of the four setting pairs".

So it is stronger in just once sense, but weaker in others.

He makes a claim about physical reality based on experiments which supposedly proved that claim. The sequence plays no role in his proof; however the direct comparison of certain settings does (without mixing in other settings, which could obscure the interpretation). I'll check out your paper tomorrow to see if I can extract relevant data from it or its references.

 

[lugita15]

Yes, what matters for me is the kind of angles that are actually tested, as required for his proof.

What do you mean "the kind of angles"? Didn't you just agree with me that the logic of the proof is unaffected by what three angles you choose?

No I ask for the data of an experiment that did what I put in bold face: with set-up I mean a protocol that matches his proof. Likely one or two were done that contain it as a subset.

Sorry, when did you put something in boldface?

Can you tell me what would or would not count as a "protocol that matches his proof"? I don't even know what you mean by protocol. Do you mean that the experiment should measure the error rate for a and c, a and b, and b and c, or do you want something more demanding?

 

[harrylin]

What do you mean "the kind of angles"? Didn't you just agree with me that the logic of the proof is unaffected by what three angles you choose?

It's the details that matter, see below. Probably that has been done, but yesterday I didn't find such a data set (to my great surprise). Maybe tomorrow.

Sorry, when did you put something in boldface?

Post #97: I made "set-up" bold-face, to stress that I talk about how the test is done.

Can you tell me what would or would not count as a "protocol that matches his proof"? I don't even know what you mean by protocol. Do you mean that the experiment should measure the error rate for a and c, a and b, and b and c, or do you want something more demanding?

Hardly more demanding than that. Getting back to my reminder of yesterday:

'Step One: Start by aligning both SPOT detectors. No errors are observed.
Step Two: Tilt the A detector till errors reach 25%. This occurs at a mutual misalignment of 30 degrees.
Step Three: Return A detector to its original position (100% match). Now tilt the B detector in the opposite direction till errors reach 25%. This occurs at a mutual misalignment of -30 degrees.
Step Four: Return B detector to its original position (100% match). Now tilt detector A by +30 degrees and detector B by -30 degrees so that the combined angle between them is 60 degrees.'

From that I get that for his argument we need at detectors (A, B) data streams from the angle pairs (a a'), (b a'), (a c), and (b c) as a minimum, and it would be nice to repeat (a a') as Herbert suggests. As experimenter I would also throw in once (b b') and (c' c) for better characterization, but it's not necessary. Moreover, typically b and c are <45° angles in opposite directions but I suppose that bigger angles are also fine.

 

[harrylin]

[..] I suppose someone who did Herbert's *experiment* wouldn't demand exactly zero error rate in the (0,0) configuration. They'd allow a small error rate. So in effect, test CHSH. CHSH looks at four orrelations. Fix one at +1, and you reduce it to Bell's inequality, which is essentially Herbert.

See arXiv:1207.5103 by RD Gill (me), I uploaded a revised version last night. It will be available from at Tue, 20 Aug 2013 00:00:00 GMT.

Hi Gill, I now looked at your revised version. Does any of your references contain the data set(s) that I'm after??