Enhancement and inhibition of acoustic spontaneous emission from a superconducting qubit: Part II Coherent control and dispersive measurement*

Hybrid platforms based on superconducting circuits and bulk acoustic wave resonators provide a compact, multi-mode geometry for bosonic control owing to the slow velocity of sound in comparison to that of light. Our experimental platform, described in the first talk, is based on thin-film Aluminum Nitride on Sapphire coupled in a flip-chip geometry to a transmon superconducting qubit. Here, we characterize the strong dispersive coupling between the transmon and bulk acoustic waves in Sapphire.

We use the dispersive coupling to spectroscopically characterize the coherence of individual phononic modes in Sapphire and demonstrate basic driven interactions with the qubit. The order of magnitude increase in the cooperativity of our devices compared with the state of the art in quantum acoustics may enable developments of compact quantum memories and transducers.