Quantum phenomena in ultra-high Q whispering gallery mode resonators and applications to quantum information systems

Kerr optical frequency combs are obtained by pumping an ultra-high Q whispering-gallery mode resonator with a continuous-wave laser. Here, we use quantum Langevin equations to investigate the non-classical behavior of these combs when pumped below and above threshold. Under threshold, we study the phenomenon of spontaneous four-wave mixing, while above threshold, we investigate the phenomenon of two-mode squeezing. For both the below- and above-threshold cases, we find that an essential parameter is the ratio between out-coupling and total losses, which directly determines the efficiency of the detected spontaneous noise or squeezing spectra.