Parity-Assisted Generation of Nonclassical States of Light in Circuit Quantum Electrodynamics

We propose a method to generate nonclassical states of light in multimode microwave cavities. Our approach considers two-photon processes that take place in a system composed of N extended cavities and an ultrastrongly coupled light-matter system. Under specific resonance conditions, our method generates, in a deterministic manner, product states of uncorrelated photon pairs, Bell states, and W states in different modes on the extended cavities. Furthermore, the numerical simulations show that the generation scheme exhibits a collective effect which decreases the generation time in the same proportion as the number of extended cavity increases. Moreover, the entanglement encoded in the photonic states can be transferred towards ancillary two-level systems to generate genuine multipartite entanglement. Finally, we discuss the feasibility of our proposal in circuit quantum electrodynamics. This proposal could be of interest in the context of quantum random number generator, due to the quadratic scaling of the output state.The authors acknowledge support from CEDENNA, Financiamiento Basal para Centros Cientificos y Tecnologicos de Excelencia FB.0807, Direccion de Postgrado USACH, FONDECYT Grant No. 1150653 and No. 1140194, Spanish MINECO/FEDER FIS2015-69983-P, Basque Government IT986-16, and Ramon y Cajal Grant RYC-2012-11391. This material is also based upon work supported by the projects OpenSuperQ and QMiCS of the EU Flagship on Quantum Technologies, and by the U.S. Department of Energy, Office of Science, Office of Advanced Scientific Computing Research (ASCR) quantum algorithm teams program, under field work proposal number ERKJ333