9
votes
Accepted
Density matrices and locality
A better way to word your final question would be: “Does this mean that the description in terms of subsystem-density matrices of A and B is not complete?”. The answer to that question is “Yes.”
...
- 1,874
6
votes
Are quantum measurements on two different particles always commutative?
Yes, they commute. However, it's not correct to talk about the commutator $[A,B]$ because these are operators defined on different Hilbert spaces.
When you have a system of two particles, the state of ...
- 81
3
votes
Are quantum measurements on two different particles always commutative?
I haven't seen it explicitly stated either, but it follows directly from definitions.
If $A$ is an observable associated with only the first particle, then by definition, it actually takes the form $...
- 104k
3
votes
Another Entanglement Question - Can you tell if the wave function of an entangled particle is collapsed?
No, you can't tell what has happened far away if all you have access to is the local system, even if your local system is entangled with the far-away system. This is a consequence of the "no-...
- 1,874
2
votes
Another Entanglement Question - Can you tell if the wave function of an entangled particle is collapsed?
Any time you make a quantum observation, the wave function of your system collapses in the sense that it gets projected onto the eigenspace of your observable that corresponds to the observed outcome. ...
- 16.3k
2
votes
Is quantum entanglement independent of measurement timing?
Yes, if you measure one of the spins as $\uparrow$, for instance, then the state of the other spin will be $\downarrow$ immediately. Entanglement is a property of the state itself, and thus has no ...
- 359
2
votes
Accepted
Is the electron pair in an orbital entangled?
Yes, they are. The search terms that you're looking for are "singlet state" (in atomic physics) or "Bell pair" (in quantum information). It would be rather difficult to extricate ...
- 1,058
2
votes
Are states of entanglement particles defined at creation?
We often create pairs of entangled particles by creating them together. For example the archetypal experiment would be to create a particle anti-particle pair, let them separate then demonstrate ...
- 359k
1
vote
Is it possible to detect entanglement by observing only one of the entangled particles?
Let V and W be the state spaces of the individual particles. An observable G acting on V acts on $V\otimes W$ by acting on the first factor, and it's easy to check that the eigenspaces are all of the ...
- 16.3k
1
vote
Is quantum entanglement independent of measurement timing?
According to relativity of simultaneously, when 2 events are space-like separated (they are too far to send signal to each other), if they are simultaneous in one observer point of view, you can ...
- 1,375
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