Measuring distance by harvesting entanglement
Grant Salton , McGill University

Abstract:

I will briefly introduce key topics in the field of relativistic quantum information, focussing mainly on the process by which entanglement can be 'harvested' from a quantum field. I will then show that entanglement harvested from a quantum field by interaction with local detectors undergoing anti-parallel acceleration can be used to measure the distance of closest approach between the two detectors. Information about the separation is stored nonlocally in the phase of the joint state of the detectors after the interaction; a single detector alone contains none. Although each detector alone sees the same thermal spectrum (due to Unruh radiation), the joint state between them may be entangled. In the vicinity of a critical distance of closest approach between the detectors, the phase of the entangled state depends sensitively on the distance. We will contrast this with the case of parallel acceleration, in which no such critical distance exists, and we will discuss the connection of this case with entanglement harvested from an expanding universe.