Does generation of a single photon distort equilibrium in the universe?

Dec 2019
3
0
USA
Entangled particles, like photons, need to be in opposite states/spins to maintain equilibrium in the universe. So, if a laser generates just one photon which is measured and confers to a spin state, is the equilibrium distorted since a paired photon was not generated to undertake an opposite state to balance? Or, when one photon is generated, second must have been generated too? In other words, impossible to generate just a single photon?
 
Jun 2016
1,357
687
England
I think you are a bit confused about entanglement (but then isn't everybody)
The paired spin state is just one of many entanglement options.
It is commonly used in experiments because it is (relatively) easy to create and detect.
 
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Apr 2015
1,227
356
Somerset, England
Just to repeat what I have said in your other entanglement thread and Woody has stat4ed here.

There are many degrees (options) of entanglement.

But since the Universe is not in equilibrium, there is no equilibrium to disturb by coherence / decoherence processes.
 
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Oct 2017
676
348
Glasgow
There are two main ways in nature to create photons:

1. Orbital electron de-excitation; and
2. Pair production

Both of these involve (electromagnetic) \(\displaystyle interactions\), in which quantum numbers are conserved. Photons have no spin quantum number (s=0), but they do have spin angular momentum (m \(\displaystyle \neq\) 0, but usually m=1). In the case of orbital electron de-excitation, the orbital electron yields a unit of angular momentum to the photon. In the case of pair production, two photons are created and the other photon has the opposite angular momentum quantum number.

So, to answer your questions:

So, if a laser generates just one photon which is measured and confers to a spin state, is the equilibrium distorted since a paired photon was not generated to undertake an opposite state to balance?
No. In a laser, electrons are excited somehow. There are different types of laser that achieve this in different ways. When a laser excites an orbital electron, it impart energy and angular momentum (the EM interaction). Then, when the orbital electron de-excites, a photon is emitted with energy and angular momentum depending on the electron level difference. Both energy and angular momentum are conserved.

Or, when one photon is generated, second must have been generated too? In other words, impossible to generate just a single photon?
In pair production, conservation of momentum requires two photons to be created, yes. In orbital electron de-excitation, no, because the angular momentum comes from the orbital electron transition.

Finally... in entanglement, if one of the entangled photons/particles is measured, its quantum numbers will be determined (e.g. s=+1/2). Then, following that measurement, it is immediately inferable that the spin of the other particle is the same but with opposite sign (e.g. s=-1/2). This is nothing special at face value until you realise that this ability to infer the state of the second particle is instantaneous, irrespective of distance. This led to to the Einstein's famous quote "spooky action at a distance".
 
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