Coherent frequency up-conversion of microwaves to the optical telecommunications band in an Er:YSO crystal

The ability to convert quantum states from microwave photons to optical photons is important for hybrid system approaches to quantum information processing. In this paper we report the up-conversion of a microwave signal into the optical telecommunications wavelength band using erbium dopants in a yttrium orthosilicate crystal via stimulated Raman scattering. The microwaves were applied to the sample using a 3D copper loop-gap resonator and the coupling and signal optical fields were single passed. The conversion efficiency was low, in agreement with a theoretical analysis, but can be significantly enhanced with an optical resonator.