Unruh-DeWitt detectors as mirrors: Dynamical reflectivity and Casimir effect

TL;DR

This paper shows how Unruh-DeWitt detectors can act as dynamic mirrors affecting quantum field behavior and Casimir energy, without fixed boundary conditions, revealing new insights into quantum field manipulation.

Contribution

It introduces a model where Unruh-DeWitt detectors mimic atom mirrors with dynamic reflectivity, impacting quantum field spectra and Casimir energy without boundary conditions.

Findings

Detectors can reflect a broad frequency range of quantum fields at late times.

A cavity with two detectors exhibits a transition from continuous to quasi-discrete spectrum.

Casimir energy density becomes negative and depends on UV cutoff and oscillator separation.

Abstract

We demonstrate that the Unruh-DeWitt harmonic-oscillator detectors in (1+1) dimensions derivative-coupled with a massless scalar field can mimic the atom mirrors in free space. Without introducing the Dirichlet boundary condition to the field, the reflectivity of our detector/atom mirror is dynamically determined by the interaction of the detector's internal oscillator and the field. When the oscillator-field coupling is strong, a broad frequency range of the quantum field can be mostly reflected by the detector mirror at late times. Constructing a cavity model with two such detector mirrors, we can see how the quantum field inside the cavity evolves from a continuous to a quasi-discrete spectrum which gives a negative Casimir energy density at late times. In our numerical calculations, the Casimir energy density in the cavity does not converge until the UV cutoff is sufficiently large, with which the two internal oscillators are always separable.