Nonlinear Microwave-optical Quantum Transduction

Microwave-optical quantum transducers are an essential part of building quantum networks as they allow remote microwave-based superconducting quantum processors to be connected by optical photons. Many transduction schemes that directly convert between the two frequency regimes have been proposed, but transduction can also be realized through quantum teleportation with entangled microwave-optical photon pairs, which has been shown to out-perform direct transduction within experimentally feasible regimes. Current entanglement-based transduction relies on the Spontaneous Parametric Down Conversion (SPDC) process to generate reliable entanglement, which could introduce unwanted double-photon pairs in the output. Here we study the possibility of generating pure single-photon pairs using SPDC with strong Kerr nonlinearity. Differing from the traditional continuous variable approach, we construct the Non-Gaussian output by cascading the emission to virtual cavities with time-dependent couplings, and show that the probability of higher order processes are suppressed exponentially with the increase of Kerr strength. To compare with the photon emission of SPDC, we also calculate the emission rate and the Glauber second order coherence function as figures of merits.