Microwave-to-optical transduction with quantum dots and surface acoustic wave microcavities

Coherent transduction of information between microwave- and optical-frequencies will likely be crucial for future long-range networks between superconducting quantum computers. Researchers have demonstrated electromechanical and optomechanical systems that are capable of this task. These systems typically comprise connected localized mechanical and optical modes, wherein the interaction is governed by moving boundary conditions or photoelastic effects. In this talk, we present a unique transducer based on InAs quantum dots (QDs) and surface acoustic wave (SAW) resonators on GaAs. The QDs act as localized atom-like light scatterers. The SAW resonators define discrete mechanical modes that parametrically interact with the QDs and are resonantly driven by microwave circuits. The naturally narrow QD resonance easily allows for operation in the so-called resolved-sideband limit. Further, the QD’s inherently large strain sensitivity offers large single-phonon optomechanical coupling rates (g₀). We first demonstrate state-of-the-art SAW cavities on GaAs; microwave characterization shows near-critical electromechanical coupling and mechanical quality factors >10,000. Using resonant and non-resonant optical spectroscopies, we experimentally demonstrate coherent microwave-optical transduction and large single-phonon coupling rates (g₀>1 MHz) in SAW microcavities. We argue that these systems are well-positioned for low-noise quantum transduction applications in the near future, and specify several design modifications to reach this goal.