Performance of Quantum Thermodynamic Cycles

Samarth Kumar, Nikhil Gupt, Shuvadip Ghosh +1 more

Debadrito Roy, Sudhir R. Jain

A quantum engine with n qubits performing thermodynamic cycles with two thermal reservoirs is presented. While such constructions have been aplenty, here we show the existence of what we term as "limit cycle" at a purely quantum level of description owing to the properties of superoperators governing the evolution of states. It is shown that the limit cycle is the same under forward and reverse protocol of cycle operations. This limit cycle becomes the basis of the quantum engine. One dimensional Ising model has been used to illustrate these ideas.

Camille L Latune

After a brief historical perspective, we introduce the key notions of work and heat for quantum systems, to then apply them to quantum engines operating on quantum Otto and Carnot cycles. The irreversible and dissipative character of the quantum Otto cycle is briefly analyzed, contrasting with the energetic optimality of the quantum Carnot cycle. The central question of quantum effects is also addressed and illustrated with several examples. Finally, the last part strives to explain the role that quantum thermodynamics plays for quantum applications and quantum technologies, particularly in relation to energy optimization and the trade-off between performances and energy costs.

Sebastian Deffner, Steve Campbell

He Xian, He Ji-Zhou, Xiao Yu-Ling

A four-level entangled quantum refrigeration cycle working with a two-qubit entangled system is proposed in this paper. Based on the first law of quantum thermodynamics and the concept of thermal entanglement, the relation between the quantum entanglement and the several thermodynamic quantities such as the heat transfer, the input work and the coefficient of performance is analyzed. It is found that the isoline of the coefficient of performance is the loop line and it no longer monotonically changes with the ratio of entanglement; in a small exchange constant J the operation region of the refrigerator is c1>c2 and in a larger exchange constant J the operation region of the refrigerator may be c1>c2 or c1c2; the maximal coefficient of performance increases as the exchange constant increases.

Raymon S. Watson, Karen V. Kheruntsyan

Advances in experimental control of interacting quantum many-body systems with multiple tunable parameters-such as ultracold atomic gases and trapped ions-are driving rapid progress in quantum thermodynamics and enabling the design of quantum thermal machines. In this work, we utilize a sudden quench approximation as a means to investigate the operation of a quantum thermodynamic Otto cycle in which multiple parameters are simultaneously controllable. The method applies universally to many-body systems where such control is available, and therefore provides general principles for investigating their operation as a working medium in quantum thermal machines. We investigate application of this multi-parameter quench protocol in an experimentally realistic one-dimensional Bose gas, as well as in the transverse-field Ising model. We find that such a multi-parameter Otto cycle, when operating as an engine, outperforms not only its constituent single-parameter Otto cycles in terms of the net work and efficiency, but also the combined net work of its constituent engine cycles when added together independently. We also find that a similar multi-parameter enhancement applies to the coefficient of performance when the Otto cycle operates as a refrigerator.