Quantum information transduction with acoustic resonators
Modern telecommunications networks make use of light in optical fibers to connect devices where information is processed in electronic circuits. Such an architecture can also be used to communicate and process quantum information. Local quantum processors based on superconducting (SC) microwave circuits are now capable of performing sophisticated tasks ranging from quantum simulation to quantum error correction. At the same time, low-loss quantum channels based on infrared (IR) light can transfer quantum information over long distances.  However, the crucial link between these two systems that would allow for the realization of a quantum network is still missing. Since quantum states are much more fragile than classical signals, quantum transduction between the electrical and optical domains must be highly efficient without introducing new sources of decoherence that interfere with the operation of the local processors or long-distance channels. 

The goal of this project is to create a quantum transducer between SC circuits and IR light using a third quantum system: sound waves in an acoustic resonator. My recent work showed that these mechanical resonators possess properties that make them highly promising for implementing a quantum transducer. They couple efficiently to both SC circuits and IR light, and can be used to store and manipulate quantum states of sound. The project will combine electromechanical and optomechanical transduction, which so far has only been implemented separately, in a single system. By developing techniques for integrating optics, acoustics, and microwave circuits at cryogenic temperatures, I will demonstrate the conversion of complex quantum states between the microwave and IR domains and use this capability to entangle remote SC quantum nodes. Reaching this goal will be the crucial first step toward using SC circuits to implement a quantum network for long-distance communications or to build a large-scale, modular quantum computer.