We propose a new method for frequency conversion of photons which is both versatile and deterministic. We show that a system with two resonators ultrastrongly coupled to a single qubit can be used to realize both single- and multiphoton frequency-conversion processes. The conversion can be exquisitely controlled by tuning the qubit frequency to bring the desired frequency-conversion transitions on or off resonance. Considering recent experimental advances in ultrastrong coupling for circuit QED and other systems, we believe that our scheme can be implemented using available technology.
@article{arxiv.1701.07973,
title = {Frequency conversion in ultrastrong cavity QED},
author = {Anton Frisk Kockum and Vincenzo Macrì and Luigi Garziano and Salvatore Savasta and Franco Nori},
journal= {arXiv preprint arXiv:1701.07973},
year = {2017}
}