Project title: On a test for non-classical gravity
Supervisors: Myungshik Kim
In our current understanding of fundamental forces, there is gravity on the one hand, that is an effect mediated by space-time which dynamics are described by the equations of general relativity, an immensely successful classical field theory. On the other hand, all other known forces have been expressed in the standard model Lagrangian and their mediating fields' dynamics are incredibly well described by quantum field theories. While both can be used at the same time, in quantum field theory in curved space-time, there remains open questions that emerge from having two radically different frameworks, namely at the Planck scale, or from the mere fact that mass-energy sources can be in spatial superpositions. This is why quantizing gravity is among the most important problems in modern fundamental physics.
However, contrary to all other known forces, there is no empirical evidence for the quantum nature of the gravitational interaction, as no observations go against general relativistic predictions. Worse yet, predictions from high energy physics show that the quantum particle of gravity, should it exist, would not be detectable in a reasonable amount of time even with detectors as massive as Jupiter.
A recent interferometric experiment proposal founded on results from quantum information theory has been put forward, in which a way to exhibit non-classical behaviours of the gravitational coupling using entanglement detection is presented. In the original proposal, unphysical ideally localized states -or positional qubits- were used.
As of now, the aim of the project is to evaluate how taking more realistic states, such as coherent, or even better, mixed thermal states, affects the protocol. Following directions would be designing better entanglement witnesses in order to decrease the amount of interaction time required before revelation, and taking into account higher order effects such as Casimir coupling.