Entangling continuous variables with a qubit array

Abstract

We show that an array of qubits embedded in a waveguide can emit entangled pairs of microwave photon beams. The quadratures obtained from a homodyne detection of these outputs beams form a pair of correlated continuous variables similarly to the EPR experiment. The photon pairs are produced by the decay of plasmon-like collective excitations in the qubit array. The maximum intensity of the resulting beams is only bounded by the number of emitters. We calculate the excitation decay rate both into a continuum of photon state and into a one-mode cavity. We also determine the frequency of Rabi-like oscillations resulting from a detuning.