Solid-state optical interconnect between distant superconducting quantum chips

We propose a design for a quantum microwave-optical photonic interface using electron spins in crystals to adiabatically swap the quantum states between a flux qubit and optical cavity that can achieve a transfer fidelity in excess of 90%. Following detailed modeling, we show that our protocol is robust against inhomogeneous broadening of the microwave and optical transitions, phase mismatch between the microwave and optical fields, and has the advantage that we can dynamically control the overall microwave-optical coupling strength in time. Using these capabilities we show how to coherently transport quantum information between two distant superconducting chips optically with a fidelity exceeding 90%.