Entanglement after the photons no longer exist

[San K]

Refer to the experiment below:

Trying to understand this phrase/sentence: "Entanglement after the photons no longer exist"

What is being entangled if the photons no longer exist?

Victor can entangled the two photons but Alice and Bob's photons are destroyed, so how can they be entangled?

The experiment is as below..

The basic setup goes like this:

Both pairs of photons are entangled, so that the two particles in the first set are entangled with each other, and the two particles in the second set are entangled with each other. Then, one photon from each pair is sent to a person named Victor. Of the two particles that are left behind, one goes to Bob, and the other goes to Alice.

But now, Victor has control over Alice and Bob's particles. If he decides to entangle the two photons he has, then Alice and Bob's photons, each entangled with one of Victor's, also become entangled with each other. And Victor can choose to take this action at any time, even after Bob and Alice may have measured, changed or destroyed their photons.

 

[DrChinese]

What is being entangled if the photons no longer exist?

The wave function exists in a fashion that defies normal definitions. So although the entangled photons no longer exist as individual entities, they are still a part of a system which continues to evolve.

Again, the key distinction is that words do not do justice to the spreading of the wave function through space-time. The result of the experiment, strange as they are, are not surprising in the sense that they are fully in keeping with traditional QM.

 

[mfb]

That looks like a variant of the delayed choice quantum eraser experiment. Bob and Alice can measure their photons, and Victor can influence the correlations in the whole setup.

http://www.nature.com/nphys/journal/v8/n6/full/nphys2294.html

 

[San K]

The wave function exists in a fashion that defies normal definitions. So although the entangled photons no longer exist as individual entities, they are still a part of a system which continues to evolve.

Again, the key distinction is that words do not do justice to the spreading of the wave function through space-time. The result of the experiment, strange as they are, are not surprising in the sense that they are fully in keeping with traditional QM.

Thanks for clarifying Dr. Chinese. Would stretching that logic not lead to infinite wavefunctions or at (the) least all interactions since big bang (assuming that happened, to begin with) reflected in the wavefunctions? ;)

Qm is mind boggling. Its tempting to assume additional dimensions to simplify the understanding of QM.

 

[mfb]

Would stretching that logic not lead to infinite wavefunctions or at (the) least all interactions since big bang (assuming that happened, to begin with) reflected in the wavefunctions? ;)

That looks a bit like the many-worlds interpretation: No collapses, just unitary evolution of the wave function (which involves the whole universe).

 

[DrChinese]

Thanks for clarifying Dr. Chinese. Would stretching that logic not lead to infinite wavefunctions or at (the) least all interactions since big bang (assuming that happened, to begin with) reflected in the wavefunctions? ;)

Qm is mind boggling. Its tempting to assume additional dimensions to simplify the understanding of QM.

Yes, so true. I don't know about the infinities part, since there is the concept of renormalization (to eliminate those). I guess as we discover more about the space-time metric we live in, we will be able to answer that more effectively.