Quantitative non-classicality of mediated interactions

Understand

In plethora of physical situations one can distinguish a mediator -- a system that couples other, non-interacting systems.

• Often the mediator itself is not directly accessible to experimentation, yet it is interesting and sometimes crucial to understand if it admits non-classical properties.
• An example of this sort that recently enjoys considerable attention are two quantum masses coupled via gravitational field.
• It has been argued that the gain of quantum entanglement between the masses indicates non-classicality of the states of the whole tripartite system.