Reconsidering Photonic Quantum Heat Engine Efficiency

Abstract

A device — referred to as a photonic quantum heat engine — was reported in Nature Photonics [J. Kim, S. Oh, D. Yang, J. Kim, M. Lee and K. An, A photonic quantum engine driven by superradiance, Nat. Photon. 16 (2022) 707–711] with an efficiency of [Formula: see text]%. Moreover, in a related News & Views contribution in the same issue [M. Kim, M. Scully and A. Svidzinsky, A supercharged photonic quantum heat engine, Nat. Photon. 16 (2022) 669–670], this device was reported to exceed the Carnot limit, an extraordinary claim. As Carl Sagan once remarked, “Extraordinary claims require extraordinary evidence.” Here, we outline the fundamental lack of empirical evidence that would be required to support such a claim, show that the actual efficiency of the device is [Formula: see text] 0% and bring to attention critical aspects of the operating physics of the device.