Quantum Entanglement Harvesting

[sanman]

An article by the University of Waterloo talks about Quantum Entanglement Harvesting and possible novel applications, such as using it to probe the structure of spacetime:

https://uwaterloo.ca/institute-for-quantum-computing/news/entanglement-harvesting-vacuum

So I understand that Spacetime and the Quantum Vacuum are 2 ways of referring to the same thing, and that the Quantum Vacuum is composed of entangled virtual particle-antiparticle pairs.

But this is the first time I'm hearing this phrase "entanglement harvesting", and I just want to better understand what it means and what its most useful
applications may be.

Quantum theory states that the quantum vacuum isn’t really empty. Quantum fluctuations of the electro-magnetic field vacuum are entangled. These fluctuations can interact locally with two space-like separated atoms and entangle them even if the two atoms never communicated with one another, or even if they never exchanged any information at all. This phenomenon is known as entanglement harvesting.

How does this entanglement harvesting work? Are they talking about in the presence of an applied electromagnetic field? Is this something that's long been known about, or is it something new?

 

[bhobba]

and that the Quantum Vacuum is composed of entangled virtual particle-antiparticle pairs.

The quantum vacuum is the ground state of the quantum fields. This virtual particle stuff is simply a name for terms in a perturbative expansion and aren't in any way real It would have been better calling them Jaberwocky because it would lead to less confusion. However things like electrons are entangled with the EM vacuum field and this leads to actual effects like spontaneous emission. Of course even that is an approximation because electrons are excitations of the electron field and the correct analysis requires QED.

The quote you gave is rather dubious, but even professional papers can take liberties with exactitude. We have a number of professors that post here. I am not one, but they often say many papers would not have passed if they were referee. My suspicion this is one - its language is certainly very suspect.

Thanks
Bill

 

[Truecrimson]

Here is the actual paper. The references in there shows that this phenomena is not new, and according to one of their references the term "entanglement harvesting" has been used in print since 2012.

Spacetime and quantum vacuum are not the same thing. The latter, as bhobba said, is the ground state of quantum fields. From what I understand, it is a normal mode of coupled harmonic oscillators, so it is unentangled in this global mode picture but it can be entangled in the tensor product basis of number states of each oscillator. There is no need to bring in virtual particles or antiparticles.

Accepting this, entanglement harvesting then is just a standard quantum information protocol that swaps entanglement in the vacuum state to the entanglement between two objects that can interact with the vacuum.