Two-tooth bosonic quantum comb for temporal-correlation sensing

TL;DR

This paper presents a bosonic quantum comb framework for analyzing temporal correlations in thermal environments, enabling noise spectroscopy and environmental probing in quantum systems.

Contribution

It introduces a two-tooth bosonic quantum comb using process-tensor formalism to characterize coherence transport and temporal correlations in bosonic environments.

Findings

Non-monotonic memory response due to interference effects

Probe can sample the absorber's population correlator

Method applicable to circuit-QED platforms for noise spectroscopy

Abstract

We introduce a two-tooth bosonic quantum comb that captures the sequential interactions between a thermal absorber and a long-lived coherent probe. The comb provides a causal, multi-time description of coherence transport, tracking how the probe records both instantaneous fluctuations and their temporal correlations. Using a process-tensor formulation, we derive closed form expressions showing that interference between the two interaction windows generates a non-monotonic memory response that reflects a fundamental competition between the absorbers thermal population and its dynamical correlations. By sweeping the temporal separation between the interaction windows, the probe directly samples the absorbers population correlator, enabling bosonic noise spectroscopy that discriminates Markovian temperature noise from slow or spectrally structured fluctuations. The approach is readily compatible with circuit-QED platforms and offers a general method for probing fluctuating bosonic environments.