ETD

• entropy production
• monitoring
• non-Markovian
• quantum thermodynamics

We study the thermalization dynamics and thermodynamics of a qubit coupled to a structured, memory-carrying environment modeled as a single bosonic mode continuously thermalized by a Markovian bath. The competition between coherent qubit-mode coupling g and thermalization rate κ is controlled by the dimensionless ratio μ=g/κ, which drives a crossover between Markovian and strongly non-Markovian regimes. In the strongly non-Markovian limit, coherent energy exchange produces transient shortcuts to local thermalization, whereby the qubit approaches its thermal state long before global equilibration. In the opposite limit, we derive an original convolution master equation with an exponential memory kernel, which reduces to a thermal GKSL equation as μ→0. The crossover between the two regimes closely mirrors the underdamped-to-overdamped transition of a classical damped oscillator.

From the thermodynamic side, we derive an original decomposition of the reduced entropy production in terms of qubit-ancilla mutual information and ancilla relative entropy, providing a quantitative fingerprint of non-Markovian corrections. We then extend this framework to the stochastic level via two monitoring protocols — Fock-state tracking and energy-exchange detection — constructing trajectory-level entropy productions and establishing fluctuation theorems tailored to each scheme. Together, these results demonstrate that a self-consistent stochastic thermodynamics can be formulated for non-Markovian open quantum systems under continuous monitoring.