Physica Scripta

Virtual temperatures, passivity, and performance bounds on quantum thermal machines

Sachin Sonkar, Ramandeep S. Johal

Published Aug 25, 2026• 0 citations

Abstract

Abstract We analyze the role of virtual temperatures in passive quantum states using majorization theory. A weighted mean virtual temperature is defined and used to compare the passive states resulting from isoenergetic and isoentropic transformations. We apply the majorization based criterion for the direction of heat flow in a quantum Otto engine, and derive a spectrum-dependent upper bound on the Otto efficiency. The upper bound which can also be related to the min-max virtual temperatures of the passive states, is illustrated for an interacting spin working medium. Thus, virtual temperatures serve as a unifying framework connecting passivity, majorization, and the optimal performance of quantum thermal machines.

DOI: 10.1088/1402-4896/ae9e98

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