Particle-field duality in QFT measurements

TL;DR

This paper explores how pointlike quantum systems coupled to fields record either field or particle aspects depending on coupling strength, introducing an exactly solvable model that bridges these regimes and reveals a tunable duality.

Contribution

It introduces a new exactly solvable model based on Quantum Brownian motion that captures the transition between field and particle measurement regimes in quantum field theory.

Findings

Strong coupling correlates with smeared field amplitudes.

Weak coupling records particle-like properties.

The model recovers relativistic Breit-Wigner resonance behavior.

Abstract

Pointlike systems coupled to quantum fields are often employed as toy models for measurements in quantum field theory. In this paper, we identify the field observables recorded by such models. We show that in models that work in the strong coupling regime, the apparatus is correlated with smeared field amplitudes, while in models that work in weak coupling the apparatus records particle aspects of the field, such as the existence of a particle-like time of arrival and resonant absorption. Then, we develop an improved field-detector interaction model, adapting the formalism of Quantum Brownian motion, that is exactly solvable. This model confirms the association of field and particle properties in the strong and weak coupling regimes, respectively. Further, it can also describe the intermediate regime, in which the field-particle characteristics `merge'. In contrast to standard perturbation techniques, this model also recovers the relativistic Breit-Wigner resonant behavior in the weak coupling regime. The modulation of field-particle-duality by a single tunable parameter is a novel feature that is, in principle, experimentally accessible.