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Title: Entanglement and quantum clocks in curved spacetime
Author: Lock, Maximilian
ISNI:       0000 0004 7969 8914
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2019
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In this thesis, we investigate how motion through a curved spacetime background affects a system's dynamics, specifically the entanglement contained between its degrees of freedom, and our ability to use the system as a clock. We incorporate both quantum theory and general relativity using quantum field theory in curved spacetime, localising the field by boundaries to describe e.g. an optical cavity. We derive the effect of boundary motion on the state of the field contained therein. A moving boundary can create particles from the vacuum in a phenomenon known as the dynamical Casimir effect; we give a description of the effect in curved spacetime. Reconsidering a common scenario, now adopting the Schwarzschild metric, we find novel particle-production resonances due to the curvature. We also discuss a potential enhancement of the effect in the phonon field of a Bose-Einstein condensate. We apply these results to a quantum model of the famous light-clock thought experiment. After motivating and reviewing the model, we show for Gaussian clock states that the discrepancy between two such clocks is state-independent, and separates into classical and quantum effects. We numerically investigate the discrepancy when one clock is held in a gravitational field and the other falls a certain distance, finding quantitative and qualitative differences from the case of classical pointlike observers. We further show that the quantum and classical effects respectively increase and decrease in magnitude with increasing gravitational field strength. We then study entanglement in a number of drop-tower scenarios, considering entanglement generated between field modes within an apparatus, and the degradation of an initially entangled state, both between spatially separated parties, and between modes contained within one apparatus. We quantify the effect via the negativity or the entanglement fidelity, as appropriate to each case. We present numerical investigations into the entanglement generated/degraded, finding novel features compared to previous investigations of non-inertial motion in flat spacetime, and discuss our results in the context of recent experiments on the subject.
Supervisor: Fuentes, Ivette ; Kim, Myungshik Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral