Universal cooling of quantum systems via randomized measurements

TL;DR

This paper introduces a universal, structure-independent quantum cooling protocol using randomized measurements, enabling effective cooling without detailed system knowledge, applicable to quantum computing and simulation.

Contribution

It demonstrates that random system-meter interactions can achieve robust cooling, relying on the rotating-wave approximation for scalable quantum control.

Findings

Cooling is achieved without system spectrum knowledge.

Resonant energy exchange dominates over heating at small interactions.

The protocol is robust, scalable, and applicable to complex quantum systems.

Abstract

Designing cooling protocols is believed to require knowledge of the system spectrum. In contrast, cooling in nature occurs whenever the system is coupled to a cold bath. How does nature know how to cool? A natural cold bath can be mimicked with a reservoir of "meter" qubits that are initialized in their ground state. We show that a quantum system can be cooled without knowledge of system details when system-meter interactions and meter splittings are chosen randomly. For sufficiently small interaction strengths and long interaction times, the protocol ensures that resonant energy-exchange processes, leading to cooling, dominate over heating. Effectively, the dynamics is then captured by the rotating-wave approximation, which we identify as the basic mechanism for robust and scalable cooling of complex quantum systems through generic, structure-independent protocols. This offers a versatile universal framework for controlling quantum matter far from equilibrium, in particular, for quantum computing and simulation.