Directional optomechanical amplifier for microwave signals
In a cavity optomechanical system, light fields interact with motion which interacts in turn with light, and vice-versa. The face of experimental optomechanics changed when, in the recent years, it adopted this so-called dynamical backaction effect as a fundamental tool. Besides enabling cooling or heating macroscopic mechanical oscillators at will, creating and detecting of non-classical states of motion, it was shown that it could be used to squeeze and amplify optical or microwave signals. Recently, the realization of multimode optomechanical systems has allowed to consider complex coupling schemes that could in particular produce non-reciprocal transport of photons. Following a recent theoretical proposal, we demonstrate a directional microwave amplifier with two on-chip superconducting resonators coupled to two vibrating membranes, using a principle analogous to the Aharonov Bohm effect: the two microwave cavities are coupled through two coupling paths which interfere differently for excitations propagating from one cavity to the other and for excitations travelling in the other direction.