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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: Quantum mystics
Date: Mon, 10 Jun 2024 18:40:51 -0000 (UTC)
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Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
> 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!
> 

(Edited for clarity—posting from my phone)
> 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 



-- 
Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC /
Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics