Thermodynamics of quantum trajectories and its implementation on a quantum computer

Quantum computers have recently become available as noisy intermediate-scale quantum devices. These machines yield a useful environment for research on quantum systems and dynamics. Building on this opportunity, we investigate open-system dynamics that are simulated on a quantum computer by coupling a system of interest to an ancilla. After each interaction the ancilla is measured, and the sequence of measurements defines a quantum trajectory. Using a thermodynamic analogy, which identifies trajectories as microstates [1], we show how to bias the dynamics of the open system in order to enhance the probability of quantum trajectories with desired properties, e.g., particular measurement patterns or temporal correlations. We discuss how such a biased, generally non-Markovian, dynamics can be implemented on a unitary, gate-based quantum computer and show proof-of-principle results on the ibmq_jakarta machine [2]. While our analysis is solely conducted on small systems, it shows a practical way for implementing biased quantum dynamics that allows to investigate fluctuations and access rare events [3].

[1] J. P. Garrahan and I. Lesanovsky, Thermodynamics of Quantum Jump Trajectories, Physical Review Letters 104, 160601 (2010)

[2] M. Cech, I. Lesanovsky and F. Carollo Thermodynamics of quantum trajectories on a quantum computer Physical Review Letters 131, 120401 (2023)

[3] F. Carollo, J. P. Garrahan, I. Lesanovsky and C. Perez-Espigares Making rare events typical in Markovian open quantum systems Physical Review A 98, 010103(R) (2018)