10:00 (CET) March 15,  Prof. Dr. Simon Haine (The Australian National University)

Title: Searching for Signatures of Quantum Gravity with Ultracold Quantum Gases


While a full theoretical quantum treatment of quantum gravity remains elusive, effective quantum field theories of gravity have been developed, by treating the quantum field as a perturbation from the classical solution. Low-energy laboratory-scale experiments are well within this perturbative regime. However, whether or not the gravitational field displays quantum properties, that is, if a quantum treatment is required at all, is a question that demands experimental resolution, with several proposed theories stating that the gravitational field may be fundamentally classical. Recently, there has been considerable interest in the possibility of low-energy experiments capable of distinguishing if the difference between a theory of gravity where the gravitational field is allowed to exist in a coherent quantum superposition, and theories where the gravitational field must remain classically valued. 

I explore the possibility of testing the quantum nature of the gravitational field with an ensemble of ultra-cold atoms. The use of many microscopic particles may circumvent some of the experimental obstacles encountered in recent proposals involving a pair of particles with mesoscopic mass. I employ multi-parameter estimation techniques, including the quantum and classical Fisher information to provide a criteria for the observability of the quantum effects, and compare to other recently proposed schemes. Crucially, I find that by preparing the appropriate initial state, interactions mediated via a quantum-valued gravitational field provide a signature that is distinct from classical gravitational interactions.


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