Coherent feedback-enhanced asymmetry of thermal process in open quantum systems: Cavity optomechanics

Entropy production is a fundamental concept in nonequilibrium thermodynamics, providing a direct measure of the irreversibility inherent in any physical process. In this work, we investigate in steady-state the enhancement of irreversibility employing coherent feedback loop. We evaluate the steady-state entropy production rate and quantum correlations by applying the quantum phase space formulation to calculate the entropy change. Our study reveals the essential contribution of coherent feedback in the thermal bath’s input-noise operators, resulting in the system being driven far from thermal equilibrium. Our analysis shows that in the small-coupling limit, the entropy production rate is proportional to the quantum mutual information. We use for application the optomechanical system of Fabry-Pérot cavity, and show that the picks of the entropy production corresponding of the heating/cooling of movable mirror are improved. Therefore, we conclude that irreversibility and quantum correlations are not independent and must be analyzed jointly. The results demonstrate the possibility of enhancement of entropy production and pave the way for promising quantum thermal applications through coherent feedback loop.

💡 Research Summary

This research presents a sophisticated investigation into the enhancement of thermodynamic irreversibility within open quantum systems through the implementation of a coherent feedback loop. At the heart of the study is the concept of entropy production, which serves as a fundamental metric for the irreversibility inherent in non-equilibrium physical processes. The authors explore how a coherent feedback mechanism can be utilized to manipulate the steady-state entropy production rate and the associated quantum correlations.

Utilizing the quantum phase space formulation, the researchers precisely calculated the entropy changes within the system. A pivotal finding of this work is the discovery that the coherent feedback loop significantly modifies the input-noise operators originating from the thermal bath. This modification is not merely a secondary effect but a primary driver that pushes the system far from its thermal equilibrium state, thereby enhancing the asymmetry of the thermal process. Furthermore, the study establishes a profound theoretical link in the small-coupling limit, demonstrating that the entropy production rate is directly proportional to the quantum mutual information. This mathematical relationship implies that the control of quantum correlations is intrinsically linked to the management of thermodynamic irreversibility.

To demonstrate the practical implications of these theoretical insights, the authors applied their framework to a cavity optomechanical system, specifically a Fabry-Pérot cavity. In this setup, the interaction between light and the mechanical motion of a movable mirror provides a platform for observing macroscopic quantum effects. The results indicate that the application of coherent feedback leads to an improvement in the peaks of entropy production during the heating and cooling cycles of the mechanical mirror. This enhancement suggests that feedback-driven control can optimize the efficiency of thermal processes in optomechanical architectures.

In conclusion, the paper asserts that irreversibility and quantum correlations are not independent phenomena but must be analyzed as an integrated whole. The ability to enhance entropy production via coherent feedback opens up new frontiers for quantum thermal engineering. These findings pave the way for the development of advanced quantum thermal applications, such as highly efficient quantum heat engines and precision quantum refrigerators, where the fine-tuning of noise and correlations is essential for operational success. This work provides a robust foundation for future research into the active control of non-equilibrium quantum thermodynamics.