Millimeter-Wave Optomechanical Circuits for Preparing Non-Gaussian States of Motion

IQC Special Seminar, Bradley Hauer, National Institute of Standards and Technology

In the current paradigm of quantum cavity optomechanics, the relatively weak parametric coupling between an electromagnetic cavity and a mechanical resonator is mediated by an external pump. While this strong cavity drive acts to enhance the optomechanical interaction, it obscures its intrinsic nonlinearity, restricting these systems to bilinear operations on Gaussian states. By increasing this coupling such that it dominates the decoherence rates of the system, one could instead use the fundamental optomechanical nonlinearity to prepare the mechanical resonator into complex, non-Gaussian states. The ability to prepare these highly non-classical states of motion has potential applications in quantum metrology, quantum information, and tests of quantum mechanics itself. In my talk, I will first present a theoretical protocol that utilizes the intrinsic optomechanical nonlinearity to dissipatively engineer non-Gaussian states of motion. By simply applying two pumps to an optomechanical cavity whose single-photon coupling exceeds its cavity loss rate, I will show that it is possible to prepare a massive mechanical resonator into a macroscopic Schrödinger cat state. I will also present my experimental efforts towards reaching this regime by improving optomechanical coupling using superconducting millimeter-wave circuits. Based on previous microwave vacuum gap capacitor designs, these devices are optimized to enhance not only their optomechanical coupling, but also their intrinsic mechanical quality factors. I will present measurements of these millimeter-wave devices at dilution refrigerator temperatures using a waveguide-coupled, cryogenic amplifier. These novel measurements of millimeter-wave optomechanical cavities demonstrate the first steps towards the ultimate goal of performing quantum-coherent control of mechanical motion at the single-photon level.

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