Frequency conversion in ultrastrong cavity QED
When atoms and photons are ultrastrongly coupled, higher-order processes, which do not conserve the number of excitations in the system, become possible. In previous work, we have shown how this can be used to realize analogs of a large number of well-known nonlinear-optics phenomena. Here, we analyze in detail a few frequency-conversion schemes based on such analogs. We consider a system with a qubit coupled ultrastrongly to two resonator modes. We show that this setup can be used to realise both single- and multiphoton frequency-conversion processes with close to unit efficiency without any strong external drive. 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.
Frequency conversion in ultrastrong cavity QED
Anton Frisk Kockum, Vincenzo Macrì, Luigi Garziano, Salvatore Savasta, and Franco Nori
arXiv:1701.07973