Realization of directional amplification in a microwave optomechanical device

Directional transmission or amplification of microwave signals is indispensable in various applications involving sensitive measurements. Using a device including two on-chip superconducting resonators and two metallic drumhead mechanical oscillators, we experimentally demonstrate how to use this generic cavity optomechanical system to non-reciprocally amplify microwave signals. Pumping this device at four distinct microwave frequencies allows to design two transmission paths for excitations from one microwave port of the device to another, that can be made to interfere constructively or destructively depending on the signals's propagation direction. As a result, we demonstrate amplification in one direction by 9 decibels and a simultaneous isolation in the opposite direction by 21 decibels.