Switching in modulated quantum oscillators beyond the rotating wave approximation.

Experiments with Josephson bifurcation amplifiers have reached the regime where the switching between different metastable states is governed by quantum fluctuations [1]. The existing theoretical analysis of the metastable decay relies on the rotating wave approximation (RWA) and gives an exponentially small switching rate [2]. Therefore if corrections to the RWA modify the switching rate, they can become substantial even where they are small. We incorporate them within a semiclassical perturbation theory in the Floquet basis. Our analytical results are corroborated by numerical calculations and suggest a switching mechanism that had been previously overlooked. \\[4pt] [1] R. Vijay et al, Rev. Sci. Instr. 80, 111101 (2009). \\[0pt] [2] M. I. Dykman and V. N. Smelyanskii, Sov. Phys. JETP 67, 1769 (1988); M. Marthaler and M. I. Dykman, Phys. Rev. A 73, 42108 (2006).