How Long Does a Photon Retain Its Spin After Dis-Entanglement?

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In summary, after dis-entanglement, on average, an event occurs that causes the photon to lose its newly created spin/state. This is illustrated by the example of Alice and Bob's entangled photons, where if Bob measures at a later time after Alice, his photon will remain in a definite state. However, according to standard QM, the photon at Bob's side is still in a superposition of spin up and down until a measurement is made.
  • #1
San K
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how long, after dis-entanglement, on average, does an event occur that causes the photon to loose its newly created spin/state?

To illustrate the above, let's say:

Alice measures her entangled photon at 10 am. She gets spin up. We all know if Bob measures at 10:000000000001 am he will get spin down.

However let's assume Bob was having beer and was a bit slow and measured his photon at say, 10:15 am...
 
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If nothing further happens to Bob's photon (i.e. interacts etc.), then it will remain spin down.

(Technically, though, when Alice measures her photon, the photon at Bob's side is still entangled with Alice's (i.e. in no definite state, according to standard QM). This is a consequence of the linearity of the Schrodinger equation.)
 
  • #3


and if bob after see his spin down change it to up, alice it will see then her spin down ?...
 
  • #4


audioloop said:
and if bob after see his spin down change it to up, alice it will see then her spin down ?...

Nope.
 
  • #5


StevieTNZ said:
(Technically, though, when Alice measures her photon, the photon at Bob's side is still entangled with Alice's (i.e. in no definite state, according to standard QM). This is a consequence of the linearity of the Schrodinger equation.)
What do you mean by "in no definite state"? 'Collapse' is instantaneous as far as we can tell at this point(>10^4 C), and we are talking about one system.
 
  • #6


Maui said:
What do you mean by "in no definite state"? 'Collapse' is instantaneous as far as we can tell at this point(>10^4 C), and we are talking about one system.

right.
 
  • #7


Maui said:
What do you mean by "in no definite state"? 'Collapse' is instantaneous as far as we can tell at this point(>10^4 C), and we are talking about one system.

By "in no definite state", I mean in a superposition of spin up and down.
 
  • #8


StevieTNZ said:
By "in no definite state", I mean in a superposition of spin up and down.



Indefiniteness is broken once a measurement is made on the system. Bob's photon cannot remain in an indefinite state(up and down).
 
  • #9


As I stated earlier, according to standard QM no measurement occurs.
 

FAQ: How Long Does a Photon Retain Its Spin After Dis-Entanglement?

What is "dis-entanglement"?

"Dis-entanglement" refers to the process of separating two quantum particles that were previously entangled. This occurs when the particles are no longer connected through a shared quantum state, and they behave independently.

What is a photon?

A photon is a fundamental particle of light that carries electromagnetic energy and has zero mass. It is the basic unit of light and is responsible for all electromagnetic interactions in the universe.

What is spin/state in relation to photons?

Spin/state refers to the intrinsic angular momentum of a particle, such as a photon. It determines how the particle interacts with magnetic fields and can have two possible values: spin up or spin down.

How is the spin/state of a photon created?

The spin/state of a photon is created through a process called polarization, where the direction of the electric field oscillation of the photon is determined. This determines the spin of the photon, which can be either vertical or horizontal.

How long does a photon retain its newly created spin/state after dis-entanglement?

The duration of a photon's spin/state after dis-entanglement is not fixed and can vary depending on the specific circumstances. In some cases, it can persist for a long time, while in others it may change quickly due to external factors such as interactions with other particles or fields.

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