Re: Quantum mystics

Martin Brown <'''newspam'''@nonad.co.uk> wrote:

On 10/06/2024 17:25, Jeroen Belleman wrote:

On 6/10/24 16:20, john larkin wrote:

 

But photon entanglement can't be explained, or even thought about, in
classic-physics terms.
 
Nor can single-photon interferance.
 
Just accept and enjoy it.

 
That's false! Entanglement and interference can easily be understood
in terms of waves and quantized detectors. It's the QM view, with its
imagined photon particle flying everywhere at once that is confusing.

 
But that world view is backed up by experiments.
 
Particles can behave as waves and waves can behave as particles
depending on the experiment. The particle isn't "everywhere at once"
either it is trapped in a spherical shell radius vt expanding around its
point of origin with the amplitude of the wavefunction representing the
chances of finding it at any particular position.
 

What size do you imagine a photon to be?

 
Depends on the wavelength of the photon but to have a well defined
frequency the amplitude envelope has to be a good few wavelengths long
and to agree with causality the leading edge must be zero until
sufficient time has passed from its emission to reaching its target. I
expect that there is a canonical shape for a photon amplitude envelope
for given df/f but I don't know what it is or if it has ever been computed.
 
This aspect of size of a photon always seemed very awkward to me when
working at 21cm neutral hydrogen and measuring what are essentially tiny
correlations in narrowband random noise from extremely remote mostly
point sources over a large number of different antenna pairs. What is
pretty clear is that the correlations of such signals are good enough
even on planetary dimensions for VLBI to work!

 

Sticking with the semiclassical picture of photodetection is good, because
it avoids almost all of the blunders made by the photons-as-billiard-balls
folk, but it doesn’t get you out of the mystery.
 
The really mysterious thing about photodetection is that a given photon (*)
 
incident on a large lossless detector gives rise to exactly one detection
event, with probability spatialy and temporally weighted by E**2.
 
Doesn’t seem so bad yet, but consider this:
If the detector is large compared with the pulse width/c, distant points on
the detector are separated by a spacelike interval.
 
That means that when point A detects it, there is no way for that
information to reach point B before the end of the pulse, when E drops to
zero, and yet experimentally point B doesn’t detect it.
 
(*) a quantized excitation of a harmonic oscillator mode of the EM field in
a given set of boundary conditions)
 
Cheers
 
Phil Hobbs