Extracting work from random collisions: A model of a quantum heat engine

Abstract

We study the statistical distribution of the ergotropy and of the efficiency of a single-qubit battery ad of a single-qubit Otto engine, respectively fuelled by random collisions. The single qubit, our working fluid, is assumed to exchange energy with two reservoirs, a non-equilibrium "hot" reservoir and a zero temperature cold reservoir. The interactions between the qubit and the reservoirs is described in terms of a collision model of open system dynamics. The qubit interacts with the non-equilibrium reservoir (a large ensemble of qudits all prepared in the same pure state) via random unitary collisions and with the cold reservoir (a large ensemble of qubits in their ground state) via a partial swap. Due to the random nature of the interaction with the hot reservoir, fluctuations in ergotropy, heat, and work are present, shrinking with the size of the qudits in the hot reservoir. While the mean, "macroscopic" efficiency of the Otto engine is the same as in the case in which the hot reservoir is a thermal one, the distribution of efficiencies does not support finite moments, so that the mean of efficiencies does not coincide with the macroscopic efficiency.

6 pages, 6 figures

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• Efficiency fluctuations in a quantum battery charged by a repeated interaction process
• Model-free optimization of power/efficiency tradeoffs in quantum thermal machines using reinforcement learning
• Efficiency of optically pumping a quantum battery and a two-stroke heat engine
• Correcting Coherent Errors by Random Operation on Actual Quantum Hardware
• Maximum Power of Coupled-Qubit Otto Engines
• Collisional charging of a transmon quantum battery
• Non-positive energy quasidistributions in coherent collision models
• Continuous Variable Structured Collision Models
• Unified trade-off optimization of quantum harmonic Otto engine and refrigerator