Experimentally probing entropy reduction via iterative quantum information transfer

TL;DR

This paper experimentally explores how iterative quantum measurement and feedback influence entropy reduction and thermodynamic costs in a quantum system, demonstrating fundamental quantum thermodynamics principles and advantages of non-Markovian feedback.

Contribution

It introduces an experimental study of entropy reduction via iterative quantum information transfer, extending quantum thermodynamics to include feedback causal structures.

Findings

Verified quantum thermodynamics laws with feedback

Demonstrated thermodynamic benefits of non-Markovian feedback

Extended theoretical framework to include feedback causal structure

Abstract

Thermodynamic principles governing energy and information are important tools for a deeper understanding and better control of quantum systems. In this work, we experimentally investigate the interplay of the thermodynamic costs and information flow in a quantum system undergoing iterative quantum measurement and feedback. Our study employs a state stabilization protocol involving repeated measurement and feedback on an electronic spin qubit associated with a Silicon-Vacancy center in diamond, which is strongly coupled to a diamond nanocavity. This setup allows us to verify the fundamental laws of nonequilibrium quantum thermodynamics, including the second law and the fluctuation theorem, both of which incorporate measures of quantum information flow induced by iterative measurement and feedback. We further assess the reducible entropy based on the feedback's causal structure and quantitatively demonstrate the thermodynamic advantages of non-Markovian feedback over Markovian feedback. For that purpose, we extend the theoretical framework of quantum thermodynamics to include the causal structure of the applied feedback protocol. Our work lays the foundation for investigating the entropic and energetic costs of real-time quantum control in various quantum systems.