An integrated microwave-to-optics interface for scalable quantum computing, part 1*

The transduction of a quantum state between microwave and optical frequencies is a promising method for scaling the size of quantum computers, allowing for entanglement links between different quantum processing units. In order to establish these links the transducer has to operate with a high efficiency, over a large bandwidth with a high repetition rate while adding less than one quantum of noise. The device must also be readily scalable to allow for operation over a large number of channels.

As a step towards this goal, we develop a fully-integrated piezo-optomechanical transducer. The device is based on a lithium-niobate-on-silicon mechanical oscillator simultaneously coupled to a tunable superconducting resonator and a silicon photonic cavity. As a result of this material combination, we can realize both large electromechanical and optomechanical coupling. Using the device, we demonstrate a bidirectional photon transduction efficiency of 0.9% for a supplied optical power of 1 μW over a bandwidth of 14.8 MHz. This scalable design is a step toward forming links between quantum computers and the creation of quantum networks.