- Entanglement harvesting between two inertial Unruh-DeWitt detectors from non-vacuum quantum fluctuations(arXiv)
Abstract : Entanglement harvesting from the quantum field is a well-known fact that, in recent times, is being rigorously investigated further in flat and different curved backgrounds. The usually understood formulation studies the possibility of two uncorrelated Unruh-DeWitt detectors getting entangled over time due to the effects of quantum vacuum fluctuations. Our current work presents a thorough formulation to realize the entanglement harvesting from non-vacuum background fluctuations. In particular, we further consider single excitation field states and a pair of inertial detectors, respectively, in (1+1) and (1+3) dimensions for this investigation. Our main observation asserts that entanglement harvesting is suppressed compared to the vacuum fluctuations in this situation. Our other observations confirm a non-zero individual detector transition probability in this background and vanishing entanglement harvesting for parallel co-moving detectors. We look into the characteristics of the harvested entanglement and discuss its dependence on different system parameters
2.Quantized mass-energy effects in an Unruh-DeWitt detector (arXiv)
Abstract : A simple but powerful particle detector model consists of a two-level system coupled to a field, where the detected particles are the field excitations. This is known as the Unruh-DeWitt detector. Research using this model has often focused on either a completely classical description of the external degrees of freedom of the detector, or a full field-theoretic treatment, where the detector itself is described as a field. Recently there has been much interest in quantum aspects of the detector’s center of mass — either described as moving in superposition along semiclassical trajectories, or dynamically evolving under a non-relativistic Hamiltonian. However, the processes of interest — the absorption or emission of field particles — necessarily change the detector’s rest mass by the amount of energy of the absorbed or emitted field quanta. Neither of the above models can capture such effects. Here we incorporate the quantization of the detector’s mass-energy into the Unruh-DeWitt model. We show that internal energy changes due to emission or absorption are relevant even in the lowest energy limit. Specifically, corrections to transition rates due to the detector’s mass changing cannot be ignored unless the entire center of mass dynamics is also ignored. Our results imply that one cannot have a consistent model of the Unruh-DeWitt detector as a massive particle without including the mass-energy equivalence.
3.Unruh-DeWitt detectors in cosmological spacetimes (arXiv)
Author : Aindriú Conroy
Abstract : We analyse the response and thermal behaviour of an Unruh-DeWitt detector as it travels through cosmological spacetimes, with special reference to the question of how to define surface gravity and temperature in dynamical spacetimes. Working within the quantum field theory on curved spacetime approximation, we consider a detector as it travels along geodesic and accelerated Kodama trajectories in de Sitter and asymptotically de Sitter FLRW spacetimes. By modelling the temperature of the detector using the detailed-balance form of the Kubo — Martin — Schwinger (KMS) conditions as it thermalises, we can better understand the thermal behaviour of the detector as it interacts with the quantum field, and use this to compare competing definitions of surface gravity and temperature that persist in the literature. These include the approaches of Hayward-Kodama, Ashtekar et al., Fodor et al., and Nielsen-Visser. While these are most often examined within the context of a dynamical black hole, here we shift focus to surface gravity on the evolving cosmological horizon.
4. Second-quantized Unruh-DeWitt detectors and their quantum reference frame transformations(arXiv)
Abstract : We generalize the Unruh-DeWitt detector model to second quantization. We illustrate this model by applying it to an excited particle in a superposition of relativistic velocities. We calculate, to first order, how its decay depends on whether its superposition of velocities is coherent or incoherent. Further, we generalize the framework of quantum reference frames to allow transformations to the rest frames of second-quantized Unruh DeWitt detectors. As an application, we show how to transform into the rest frame of a decaying particle that, in the laboratory frame, is in a linear superposition of relativistically differing velocities.