Clock-Driven Quantum Thermal Engines

TL;DR

This paper introduces a quantum clock-based model for autonomous thermal engines that can perform arbitrary energy-conserving transformations with high accuracy, aligning with thermodynamic laws and eliminating intrinsic costs of control.

Contribution

The authors develop a quantum clock framework enabling autonomous engines to implement any energy-conserving unitary without degrading the clock, advancing quantum thermodynamics.

Findings

Exact implementation of energy-conserving unitaries without clock degradation

Approximate realization of general unitaries with a quantum work storage

Autonomous machines match the thermodynamic efficiency of controlled ones

Abstract

We consider an isolated autonomous quantum machine, where an explicit quantum clock is responsible for performing all transformations on an arbitrary quantum system (the engine), via a time-independent Hamiltonian. In a general context, we show that this model can exactly implement any energy-conserving unitary on the engine, without degrading the clock. Furthermore, we show that when the engine includes a quantum work storage device we can approximately perform completely general unitaries on the remainder of the engine. This framework can be used in quantum thermodynamics to carry out arbitrary transformations of a system, with accuracy and extracted work as close to optimal as desired, whilst obeying the first and second laws of thermodynamics. We thus show that autonomous thermal machines suffer no intrinsic thermodynamic cost compared to externally controlled ones.