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arXiv:2206.11816 · Physical Review A

Cohering and decohering power of massive scalar fields under instantaneous interactions

Nikolaos K. Kollas, Dimitris Moustos, Miguel R. Muñoz

Published Feb 13, 2023• 6 citations
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Abstract

Employing a nonperturbative approach based on an instantaneous interaction between a two-level Unruh-DeWitt detector and a massive scalar field, we investigate the ability of the latter to generate or destroy coherence in the detector by deriving the cohering and decohering power of the induced quantum evolution channel. For a field in a coherent state a previously unobserved effect is reported in which the amount of coherence that the field generates displays a revival pattern with respect to the size of the detector. Extending previous results into the nonperturbative regime of an arbitrary coupling strength, it is demonstrated that in the case of a thermal field with a positive mass a detector initialized in a maximally coherent state experiences a smaller degree of decoherence after its interaction with the field, compared to the massless case. In both examples for a suitable choice of detector radius, field energy, and coupling strength it is possible to infer the mass of the field by either measuring the coherence present in the detector in the case of an interaction with a coherent field or the corresponding decoherence of a maximally coherent state in the case of a thermal field. In view of recent advances in the study of Proca metamaterials, these results suggest the possibility of utilizing the theory of massive electromagnetism for the construction of novel applications for use in quantum technologies.

DOI
10.1103/physreva.107.022420

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Employing a nonperturbative approach based on an instantaneous interaction between a two-level Unruh-DeWitt detector and a massive scalar field, we investigate the ability of the latter to generate or destroy coherence in the detector by deriving the cohering and decohering power of the induced quantum evolution channel. For a field in a coherent state a previously unobserved effect is reported in which the amount of coherence that the field generates displays a revival pattern with respect to the size of the detector. Extending previous results into the nonperturbative regime of an arbitrary coupling strength, it is demonstrated that in the case of a thermal field with a positive mass a detector initialized in a maximally coherent state experiences a smaller degree of decoherence after its interaction with the field, compared to the massless case. In both examples for a suitable choice of detector radius, field energy, and coupling strength it is possible to infer the mass of the field by either measuring the coherence present in the detector in the case of an interaction with a coherent field or the corresponding decoherence of a maximally coherent state in the case of a thermal field. In view of recent advances in the study of Proca metamaterials, these results suggest the possibility of utilizing the theory of massive electromagnetism for the construction of novel applications for use in quantum technologies.
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Abstract We explore the quantum coherence between a pair of entangled Unruh–DeWitt detectors, interacting with a quantum field, using a nonperturbative approach in a (3+1)-dimensional Minkowski spacetime with instantaneous switching ( δ\delta δ δ -switching). It is intriguing to observe that for a maximally entangled state, increasing the coupling strength enhances the detectors’ initial quantum coherence while simultaneously causing a monotonic decrease in their initial entanglement. This reveals a remarkable phenomenon: through nonperturbative interactions, entangled Unruh–DeWitt detectors can exhibit a dual effect-amplifying quantum coherence while degrading quantum entanglement. This finding stands in stark contrast to previous studies based on perturbative methods or Gaussian switching functions, which generally concluded that interactions between detectors and the field lead to a simultaneous degradation of quantum coherence and entanglement due to environmental decoherence. Notably, while initially separable detectors successfully harvest quantum coherence from the vacuum, entanglement extraction remains fundamentally prohibited. These contrasting behaviors underscore the fundamental distinction between coherence and entanglement as quantum resources, and highlight their complementary roles in field-detector interactions.
Abstract We study, in the framework of open quantum systems, the entanglement dynamics for a quantum system composed of two uniformly accelerated Unruh-Dewitt detectors interacting with a bath of massive scalar fields in the Minkowski vacuum. We find that the entanglement evolution for the quantum system coupled with massive fields is always slower compared with that of the one coupled with massless fields, and this time-delay effect brought about by the field being massive can however be counteracted by a large enough acceleration, in contrast to the case of a static quantum system in a thermal bath, where this time delay is not affected by the temperature. Remarkably, the maximal concurrence of the quantum system generated during evolution may increase with acceleration for any inter-detector separation while that for static ones in a thermal bath decreases monotonically with temperature, and this can be considered as an anti-Unruh effect in terms of the entanglement generated.
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We study the effects of motion, on the amount of coherence extracted onto an Unruh-DeWitt detector, modeled as a two-level system, when it interacts with a massless scalar coherent field in 1+11+11+1 Minkowski spacetime. We observe that compared to a detector at rest, for certain values of the initial energy of the field and the duration of the interaction, the amount extracted is larger for a detector moving with constant speed or uniform acceleration. This ``swelling'' of coherence becomes more intense for increasing values of its velocity and acceleration, and is mostly observed for short interaction durations, when the energy of the field is larger compared to that of the detector, and for longer interaction durations but smaller field energies. As a consequence, the rate at which coherence is lost, is sometimes slower for a moving detector than for a detector at rest.
In this work, we investigate the interaction between a uniformly accelerated single qubit and a fermionic spinor field. Here we consider both the massless and the massive fermionic spinor fields. The qubit-field interaction occurs over a finite time and was evolved via perturbation theory. This approach yields the transition probability rates, from which we subsequently evaluate the quantum coherence of an Unruh-DeWitt (UDW) detector initially prepared in a qubit state. Our findings reveal that the UDW detector responds more when coupled with the fermionic field, and consequently, quantum coherence (for the fermionic case) degrades much more rapidly when compared to the case of the qubit linearly coupled with the scalar field. Moreover, the analysis suggests that particle mass plays a protective role against Unruh-induced decoherence as the rest mass energy becomes comparable to the detector's energy-level spacing, the detector's excitation probability and response decreases, which leads to the mitigation of quantum coherence degradation in accelerated quantum systems.