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. 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 three-dimensional 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.