Manipulating heat flow in quantum devices

There has been significant interest recently in using complex quantum systems to create effective nonreciprocal dynamics. Theoretical proposals have been put forward for the realization of artificial magnetic fields for photons and even phonons; experimental progress is fast making these proposals a reality. Much work has concentrated on the use of such systems for controlling the flow of signals, e.g., to create isolators or directional amplifiers for optical signals. In this paper, we build on this work but move in a different direction. We develop the theory and discuss a potential realization for the controllable flow of heat in quantum systems. We demonstrate theoretically that the observation of unidirectional flow of heat is possible within quantum cascaded systems. Viewing an optomechanical cavity platform as a cascaded system we show here that one can ultimately control the direction of the heat flow. By appropriately engineering the mechanical resonator, which acts as an artificial reservoir, heat flow can be constrained to a desired direction, yielding a thermal rectifier. The proposed quantum heat rectifier could potentially be used to develop devices such as a thermal modulator, a thermal router, and a thermal amplifier for nanoelectronic devices and superconducting circuits.