Non-Markovian Quantum Dynamics in Strongly Coupled Multimode Cavities Conditioned on Continuous Measurement

TL;DR

This paper develops an exact formalism for understanding how continuous measurement affects information gain and state estimation in strongly coupled multimode cavity QED systems, addressing a key challenge in non-Markovian quantum dynamics.

Contribution

It introduces a conditioned hierarchy of equations of motion for non-Markovian open quantum systems, enabling precise analysis of measurement effects in strongly coupled multimode cavities.

Findings

Enhanced spin squeezing via measurement and feedback.

Demonstrated how different monitoring schemes influence information gain.

Provided a framework for exact conditioned state description in non-Markovian regimes.

Abstract

An important challenge in non-Markovian open quantum systems is to understand what information we gain from continuous measurement of an output field. For example, atoms in multimode cavity QED systems provide an exciting platform to study many-body phenomena in regimes where the atoms are strongly coupled amongst themselves and with the cavity, but the strong coupling makes it complicated to infer the conditioned state of the atoms from the output light. In this work we address this problem, describing the reduced atomic state via a conditioned hierarchy of equations of motion, which provides an exact conditioned reduced description under monitoring (and continuous feedback). We utilise this formalism to study how different monitoring for modes of a multimode cavity affects our information gain for an atomic state, and to improve spin squeezing via measurement and feedback in a strong coupling regime. This work opens opportunities to understand continuous monitoring of non-Markovian open quantum systems, both on a practical and fundamental level.