Aspect's Experiment Was Flawed

[Hans de Vries]

W Have a look at their website
http://people.whitman.edu/~beckmk/QM/

Experiments like the Quantum Eraser may turn out to be much
more effective in convincing people:

http://people.whitman.edu/~beckmk/QM/qe/qe.pdf

Switching an Interference Pattern on and off at one place
by manipulating a \lambda/2 Half-Wave plate at another place,
in another beam, that went the other way, to never to
go back to the place were the interference happens...


Regards, Hans

 

[Nereid]

To add one small comment to vanesch's post (and thanks to Dr Chinese for finding those 'old' threads): fortunately, eating an elephant is easier if you take it one bite at a time.

If Caroline (or anyone else) wants to develop an alternative, it may be sensible to start with something 'easy', and just do an OOM (a.k.a. back of the envelope) calculation. It's highly likely that if your favourite alternative doesn't come within an OOM or two, it won't work out when you do the detailed calculations ... best to avoid wasting more time on that; put it to one side, and try another. The good thing about OOMs is that they can often (usually?) be done in a day or two.

 

[vanesch]

If Caroline (or anyone else) wants to develop an alternative, it may be sensible to start with something 'easy', and just do an OOM (a.k.a. back of the envelope) calculation. It's highly likely that if your favourite alternative doesn't come within an OOM or two, it won't work out when you do the detailed calculations ... best to avoid wasting more time on that; put it to one side, and try another. The good thing about OOMs is that they can often (usually?) be done in a day or two.

I am indeed absolutely in favour of that - it would be extremely exciting to see a working alternative. My personal problem with it is a problem of motivation: I'm so convinced that it won't work out that I cannot spend much effort on it. But people like Caroline, who are convinced that 99% of all physicists are deluding themselves since about 80 years now, should jump on the enormous occasion that presents itself to them. I tried to point that out. My intuition would be that any local realist theory would be computationally simpler than quantum theory, and if that is the case, it would be a revolution in computational chemistry, solid state physics and so on. Their methods would be monstruously more efficient. Think of the power of it, to model, say, macromolecules and their interactions!

However, they concentrate themselves just on arguing that "there might STILL be possibilities to develop alternatives" without presenting any. The only one I've seen is Stochastic Electrodynamics. This is essentially Maxwell's electrodynamics, together with the postulate that we are exposed to radiation which comes down to half a photon in each mode, and the argument that photodetectors are calibrated to "observe" what goes beyond this intensity. I know a bit about it, but before it can convince me, it should indeed first predict "basic" stuff where intuition says they will have difficulties, like with thermodynamics (given the huge flux of energy, how come that we don't boil off any glass of water in no time - probably naive, but these things should be addressed). I'm not very impressed with its success of demonstrating the ability to explore the efficiency loopholes in the Aspect like experiments, because _it has been invented for that purpose_. I would be more impressed if it shows that it fits in with the rest of physics.
Stochastic Electrodynamics, together with a classical Dirac field is supposed to supplant QED, and seems to make a correct prediction of the Lamb shift (Barut) (I didn't verify it) if you leave out the stochastic part ; however it doesn't even arrive at predicting the existence of the electron, and I challenged them to come up with the correct spectrum for Helium.

So we get a lot of blahblah on how there are still possibilities for local realist theories etc... but we don't get to see any that work! It is not even a matter of OOM calculations, there simply ISN'T any proposition of an alternative. Just an argument that its potential existence is not yet 100% ruled out yet. Big deal.

cheers,
Patrick.

 

[Caroline Thompson]

I am indeed absolutely in favour of that - it would be extremely exciting to see a working alternative. My personal problem with it is a problem of motivation: I'm so convinced that it won't work out that I cannot spend much effort on it. But people like Caroline, who are convinced that 99% of all physicists are deluding themselves since about 80 years now, should jump on the enormous occasion that presents itself to them.

The classical explanation of actual "quantum eraser" experiments does not require any new model, once you've allowed for the properties of outputs from PDC sources. I have no theory of the physics of what goes on in a nonlinear crystal, but have reason to think that nobody else has either! I disagree with the Stochastic Electrodynamics explanation as well as with quantum theory. Can't we go back to the situation that existed 200 years ago when they first started trying to explain the polarisation properties of "iceland spar"? Various people had various ideas, which were discussed and tested. It was admitted that we did not know the truth!

Anyway, the absence of a satisfactory theory of the physics of the interaction of light with nonlinear crystals does not prevent us using them for interesting experiments. Instead of theory, though, we have to rely on the observed behaviour to find the empirical laws governing the output.

Unfortunately the quantum theorists have, it seems, from an early stage decided on their model and insisted on interpreting all that they see within this narrow framwork! This has led them into all sorts of apparent paradoxes, quantum erasers being just one of them.

My understanding of the properties of a particular class of PDC output -- that produced in the "degenerate case", when the frequencies of both "photons" are the same -- was initially a logical deduction from experiments on "induced coherence". The key properties are covered in:

Thompson, C H, “Rotational invariance, phase relationships and the quantum entanglement illusion”, http://arxiv.org/abs/quant-ph/9912082​

and a paper I'm on the point of putting on my web site.

I think I'd better break off from PhysicsForum to do this! The paper is:

Homodyne detection and parametric down-conversion: a classical approach applied to proposed “loophole-free” Bell tests​

Don't worry too much if you've never met "homodyne detection" before. If you haven't met parametric down-conversion, though, perhaps now is the time to remedy the situation!

Caroline
http://freespace.virgin.net/ch.thompson1/

 

[vanesch]

Unfortunately the quantum theorists have, it seems, from an early stage decided on their model and insisted on interpreting all that they see within this narrow framwork!

And guess what ? This narrow framework has, up to now, always correctly predicted all experimental outcomes (which is the aim of a scientific theory). I'd be happy to know any narrow or broad framework which does the same, for the reasons I already explained: it might open up new ways of handling problems, lead to new calculational techniques etc...
Unfortunately, I don't know of ANY other such framework.

 

[Caroline Thompson]

And guess what ? This narrow framework has, up to now, always correctly predicted all experimental outcomes (which is the aim of a scientific theory). I'd be happy to know any narrow or broad framework which does the same, for the reasons I already explained: it might open up new ways of handling problems, lead to new calculational techniques etc...
Unfortunately, I don't know of ANY other such framework.

When it comes to "quantum optics" experiments, the framework you need is local realism plus a classical wave model of light plus empirical functions to model the behaviour of apparatus such as beamsplitters and detectors. Oh, and you also need empirical functions to model the output from pumped nonlinear crystals. Given these, there are no special calculational difficulties.

I wonder if you have encountered the following useful little handbook on polarisation?

Shurcliff, W A and Ballard, S S, "Polarized Light", Van Nostrand 1964​

You can deduce from this how the notions of "projection operators" and the use of matrices came into quantum theory. They were there already in classical theory. The difference is that in classical theory it is accepted that the matrices won't give you exactly correct answers -- that you have to use empirical results in real applications.

Anyway, further to this morning's message, you can now see my new paper on my web site. I had hoped to get it in HTML as well as pdf format but I think maybe I've exceeded my web space. The diagrams in the HTML version don't work. The paper illustrates once again my approach to the analysis of real optical experiments. I don't attempt to analyse any other kind but do strongly suspect that something equivalent is needed in other areas of fundamental physics.

Caroline
http://freespace.virgin.net/ch.thompson1/