Thermally driven quantum refrigerator autonomously resets superconducting qubit

TL;DR

This paper demonstrates an autonomous quantum absorption refrigerator using superconducting circuits that cools a qubit below the temperature of available baths, enabling effective qubit reset for quantum computing.

Contribution

It introduces a novel superconducting circuit-based quantum refrigerator that autonomously cools a qubit using engineered three-body interactions and thermal gradients.

Findings

Successfully cooled a transmon qubit below 22 mK

Achieved qubit reset without external feedback

Demonstrated practical application of quantum thermodynamics

Abstract

Although classical thermal machines power industries and modern living, quantum thermal engines have yet to prove their utility. Here, we demonstrate a useful quantum absorption refrigerator formed from superconducting circuits. We use it to cool a transmon qubit to a temperature lower than that achievable with any one available bath, thereby resetting the qubit to an initial state suitable for quantum computing. The process is driven by a thermal gradient and is autonomous, requiring no external feedback. The refrigerator exploits an engineered three-body interaction between the target qubit and two auxiliary qudits. Each auxiliary qudit is coupled to a physical heat bath, realized with a microwave waveguide populated with synthesized quasithermal radiation. If the target qubit is initially fully excited, its effective temperature reaches a steady-state level of approximately 22~mK, lower than what can be achieved by existing state-of-the-art reset protocols. Our results demonstrate that superconducting circuits with propagating thermal fields can be used to experimentally explore quantum thermodynamics and apply it to quantum information-processing tasks.