Multimode Entanglement Generation in a Parametric Superconducting Cavity

Parametric processes in microwave system are a source of nonclassical radiation with a number of potential applications in quantum information processing. Here we have implemented and experimentally verified a source of entangled microwave fields. Implementing a tunable, multimode microwave resonator with 3 modes in the common 4-12 GHz range, we performed two-mode parametric down-conversion between pairs of modes and observed the induced correlations in their voltage quadratures. With the system gain and noise calibrated using a shot noise tunnel junction, we have verified pairwise entanglement among the frequency modes. By introducing a second pump tone, its possible to simultaneously observe correlations between all 3 modes. We study the possibility of generating multimode entanglement in this way.