A mechanical qubit

Strong nonlinearities at the single-quantum level are important resources for quantum technologies. While they are widely used in electromagnetic systems, it has been difficult to engineer such strong interactions between phonons due to the weak intrinsic nonlinearity of most mechanical systems. I will present the realization of the single-phonon nonlinear regime in a solid-state mechanical resonator. This allows us to operate a mode of the resonator as a mechanical qubit, for which we demonstrate initialization, readout, and a full set of single-qubit gates. I will discuss how our results can be applied towards using mechanical systems for quantum sensing and tests of fundamental physics.