Experimental realization of a quantum heat engine based on dissipation-engineered superconducting circuits

TL;DR

This paper reports the first experimental realization of a quantum heat engine using superconducting circuits, demonstrating controlled thermodynamic cycles and measuring positive output power and efficiency, thus validating quantum thermodynamics models.

Contribution

It introduces a superconducting circuit-based quantum heat engine with a tunable heat reservoir and implements a quantum Otto cycle, advancing experimental quantum thermodynamics.

Findings

Successful implementation of a quantum Otto cycle in superconducting circuits

Measurement of positive output power and efficiency consistent with theoretical models

Advancement in controlling dissipation-engineered thermal environments

Abstract

Quantum heat engines (QHEs) have attracted long-standing scientific interest, especially inspired by considerations of the interplay between heat and work with the quantization of energy levels, quantum superposition, and entanglement. Operating QHEs calls for effective control of the thermal reservoirs and the eigenenergies of the quantum working medium of the engine. Although superconducting circuits enable accurate engineering of controlled quantum systems, beneficial in quantum computing, this framework has not yet been employed to experimentally realize a cyclic QHE. Here, we experimentally demonstrate a quantum heat engine based on superconducting circuits, using a single-junction quantum-circuit refrigerator (QCR) as a two-way tunable heat reservoir coupled to a flux-tunable transmon qubit acting as the working medium of the engine. We implement a quantum Otto cycle by a tailored drive on the QCR to sequentially induce cooling and heating, interleaved with flux ramps that control the qubit frequency. Utilizing single-shot qubit readout, we monitor the evolution of the qubit state during several cycles of the heat engine and measure positive output powers and efficiencies that agree with our simulations of the quantum evolution. Our results verify theoretical models on the thermodynamics of quantum heat engines and advance the control of dissipation-engineered thermal environments. These proof-of-concept results pave the way for explorations on possible advantages of QHEs with respect to classical heat engines.