Unravelling Metastable Markovian Open Quantum Systems

TL;DR

This paper investigates the dynamics of metastable Markovian open quantum systems by analyzing their stochastic trajectories, revealing classical and quantum metastability phenomena, and demonstrating the usefulness of quantum reset processes for understanding these systems.

Contribution

It introduces a trajectory-based analysis of metastability in open quantum systems, including classical and quantum examples, and highlights the role of quantum reset processes in this context.

Findings

Classical metastable phenomenology observed in a three-state model.

Quantum metastability characterized by a decoherence-free subspace in a two-qubit model.

Quantum reset processes facilitate the analysis of quantum trajectories in metastable systems.

Abstract

We analyse the dynamics of metastable Markovian open quantum systems by unravelling their average dynamics into stochastic trajectories. We use quantum reset processes as examples to illustrate metastable phenomenology, including a simple three-state model whose metastability is of classical type, and a two-qubit model that features a metastable decoherence free subspace. In the three-state model, the trajectories exhibit classical metastable phenomenology: fast relaxation into distinct phases and slow transitions between them. This extends the existing correspondence between classical and quantum metastability. It enables the computation of committors for the quantum phases, and the mechanisms of rare transitions between them. For the two-qubit model, the decoherence-free subspace appears in the unravelled trajectories as a slow manifold on which the quantum state has a continuous slow evolution. This provides a classical (non-metastable) analogue of this quantum effect. We discuss the general implications of these results, and we highlight the useful role of quantum reset processes for analysis of quantum trajectories in metastable systems.