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arXiv · 1905.08010

Schrödinger cats and steady states in subharmonic generation with Kerr nonlinearities

Feng-Xiao Sun·Qiongyi He·Qihuang Gong·Run Yan Teh·Margaret D. Reid·Peter D. Drummond
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Abstract

We discuss general properties of the equilibrium state of parametric down-conversion in superconducting quantum circuits with detunings and Kerr anharmonicities, in the strongly nonlinear regime. By comparing moments of the steady state and those of a Schrödinger cat, we show that true Schrödinger cats cannot survive in the steady state if there is any single-photon loss. A delta-function 'cat-like' steady-state distribution can be formed, but this only exists in the limit of an extremely large nonlinearity. The steady state is a mixed state, which is more complex than a mixture or linear combination of delta-functions, and whose purity is reduced by driving. We expect this general behaviour to occur in other driven, dissipative quantum subharmonic non-equilibrium open systems.

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Feng-Xiao Sun, Qiongyi He, Qihuang Gong, Run Yan Teh, Margaret D. Reid, Peter D. Drummond. 2019-08-09. Schrödinger cats and steady states in subharmonic generation with Kerr nonlinearities. https://doi.org/10.1103/physreva.100.033827

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