Erbium ion quantum register operated with a single microwave photon detector

Erbium ion embedded in crystal is a promising candidate for quantum information processing for its unique properties, such as optical transition at telecom band and large magnetic dipole. Erbium nuclear spin has long coherence time and is ideal for working as quantum memories. A hybrid quantum register formed by erbium electron spin, intrinsic nuclear spin and nearby nuclear spins in the host crystal combining fast control, high-fidelity readout and long memory time will have huge capacities in quantum applications, such as quantum computing and quantum communication. Previous spin-based quantum registers rely on the spin-dependent photoluminescence, which is system specific. In this project, we propose to realize erbium ion quantum register operated with a single microwave photon detector which is based on a superconducting transom qubit and works in principle for any spin system. This project will enable interface between quantum register and microwave photons, and pave the way for more sophisticated quantum applications of erbium ions, long-distance spin-spin entanglement, and hybrid quantum information platforms.