Particle detectors and the zero mode of a quantum field

TL;DR

This paper investigates how the zero mode of a quantum field influences particle detector responses, showing it can be minimized through specific initial state tuning, with implications for various detector motions.

Contribution

It provides a detailed analysis of the zero mode effects on particle detectors, including methods to suppress these effects in different scenarios.

Findings

Zero mode impact is nonvanishing but can be negligible in certain limits.

Tuning the initial state of the zero mode can suppress its effects for derivative-coupling detectors.

Regularity of the ultrarelativistic limit is demonstrated for inertial detectors with arbitrary velocity.

Abstract

We study the impact of the zero-mode of a quantum field on the evolution of a particle detector. For a massless scalar field in a periodic cavity, we show that the impact of the zero mode on the Unruh-DeWitt detector and its derivative-coupling generalisation is necessarily nonvanishing but can be made negligible in some limits, including those commonly occurring in non-relativistic quantum optics. For the derivative-coupling detector this can be accomplished by just tuning the zero mode's initial state, but the standard Unruh-DeWitt detector requires a more subtle and careful tuning. Applications include an inertial detector with arbitrary velocity, where we demonstrate the regularity of the ultrarelativistic limit, and a detector with uniform acceleration.