Gravity waves vs electromagnetic waves

RF waves have quanta so tiny that we can't detect them, so QM doesn't bother us.

The size of the quanta doesn't matter.

There is no need whatever to invoke QM to explain this experiment. The only aspect that requires quanta are the detectors, where the EM waves dislodge discrete charges randomly, with an energy that depends only on the EM energy's frequency, and nothing else. That's the *only* place where QM has something useful to say.

If there's plenty of light, even that becomes moot. (This experiment required electron-multiplying CCD cameras.)

Jeroen Belleman

In a beam splitter interferometer, when a photon is detected, all the split-up waves everywhere in the system are magically and instantly gathered up and dumped in one spot. That is pretty weird.

One real-life electronic QM effect is tunneling, which can be measured in practical volts and amps.

QM has a habit of projecting the calculation of a probability distribution onto a single event. That's what the "collapse of the wavefunction" really is. That's just silly. Expressed as you do above, it's obfuscation.

Yes, tunneling is one way of looking at gross non-linearity. Another fertile ground for quantum mysticisms.

Jeroen Belleman

The wavefunction is complex-valued, though, and the probability distribution is its squared modulus. That makes all the coherent effects go away when an event is detected.

I agree that the Copenhagen and many-worlds interpretations are mysticism. Bohr especially fell for a bunch of Eastern crapola. But tunnelling is no more mystical than the antireflection coating on your glasses--the math is almost identical.

Cheers

Phil Hobbs

Are we referring to the same thing? I can see how reflections between layers can affect the phase such that it looks like we have FTL transmission, but I see similar claims from people sending light through a saturating medium. The latter surely doesn't use the same math?

(I've been wanting to build a pulse amplifier with negative delay based on that idea, just to tweak some colleagues, but I never yet got round to doing it.)

Jeroen Belleman

We're talking about tunnelling, not FTL. There's nothing acausal going on, it's just patching solutions to the Schroedinger equation with a varying potential. I spent some years building devices based on tunnelling through a nearly square-well potential. The math is identical to an AR coating--the refractive index is a good analogue to the classical potential.

Negative group delay != time machine. You can sometimes have the first, but never the second.

Cheers

Phil Hobbs

Yeah tunneling seems pretty straight forward. I've done a little CPT, (not lately) and that is QM magic, at least to me. They mix two atomic states, with the interacting EM field (light from a laser, typically), describe it in terms of raising and lower operators, ... and find some trapped state... atoms disappear optically from the beam*. You then mix in (the ever present) B-field and .... look out.

Perhaps there is a classical analog...

But QM (to me) is the easiest way to describe it. (And I struggle with that description too.)

Jeroen, QM is at least as "real" as classical physics. Bell's inequality is in ~100 US physics departments... (Maybe not all working.) These weird extended QM states are real... as far as we can tell.

The easiest way to know the shot noise is to count photons. George H.

(*as well as the trapped state, there's some positive combination.)

Or quarter-wave matching sections in RF transmission lines, same idea.

Don't get me wrong, I'm a firm believer in causality!

Jeroen Belleman