High-Speed Quantum Interface with a Quantum Dot Molecule Coupled to a Superconducting Resonator*

Quantum transduction between optical and microwave photons is a key element of quantum networks. An optically-active quantum dot molecule (QDM) has a large electric dipole moment which can couple to microwave (MW) photons in a superconducting (SC) resonator [1]. In our scheme, the following features with a large MW coupling strength realize fast and efficient transduction: (i) a low-Q asymmetric optical cavity encapsulating the QDM ensures high-efficient absorption of incoming optical photons; (ii) fast radiative decay of the QDM finishes the transduction in nanosecond time scales; (iii) the radiative decay channel emits heralding photons upon success of the transduction.
We fabricate an onchip hybrid device consisting of a QDM and a SC resonator and demonstrate a large MW coupling strength. With a modest device improvement, we estimate that a large conversion bandwidth of over 100 MHz with high conversion efficiency is feasible.
[1] Y. Tsuchimoto et. al., Phys. Rev. B 96, 165312 (2017)