Entangling the optical frequency comb: Simultaneous generation of multiple 2x2 and 2x3 continuous-variable cluster states in a single optical parametric oscillator

We report on our research effort to generate large-scale multipartite optical-mode entanglement using as few physical resources as possible. We have previously shown that cluster-and GHZ-type N-partite continuous-variable entanglement can be obtained in an optical resonator that contains a suitably designed second-order nonlinear optical medium, pumped by at most O(N-2) fields. In this paper, we show that the frequency comb of such a resonator can be entangled in an arbitrary number of independent 2 x 2 and 2 x 3 continuousvariable cluster states by a single optical parametric oscillator pumped by just a few optical modes.