Unruh phenomena and thermalization for qudit detectors

TL;DR

This paper investigates how qudit detectors, which have multiple energy levels, respond to Unruh phenomena and compares their thermalization behavior to traditional qubit detectors, revealing limitations of detailed balance as an indicator.

Contribution

It introduces and analyzes qudit detector models for Unruh phenomena, highlighting the limitations of the detailed balance condition in higher-dimensional systems compared to qubits.

Findings

Qudit detectors have multiple transition channels affecting thermalization.

Detailed balance condition has limitations for qudit models.

Analysis of spin-1 and Heisenberg-Weyl based qutrit detectors.

Abstract

We study Unruh phenomena for a qudit detector coupled to a quantized scalar field, comparing its response to that of a standard qubit-based Unruh-DeWitt detector. We show that there are limitations to the utility of the detailed balance condition as an indicator for Unruh thermality of higher-dimensional qudit detector models. This can be traced to the fact that a qudit has multiple possible transition channels between its energy levels, in contrast to the 2-level qubit model. We illustrate these limitations using two types of qutrit detector models based on the spin-1 representations of $SU(2)$ and the non-Hermitian generalization of the Pauli observables (the Heisenberg-Weyl operators).