Emmanuel Flurin, Nicolas Roch, Francois Mallet, Michel H. Devoret, Benjamin Huard
Pairs of entangled electromagnetic beams propagating on physically separated channels, the continuous variable version of Einstein-Podolsky-Rosen (EPR) states, constitute an essential resource in quantum information processing, communication and measurements. We have performed an interference experiment demonstrating the production and measurement of EPR states of microwave light using non-degenerate Josephson mixers. Driven by a pump tone, a first mixer generates a pair entangled beams out of vacuum quantum noise. A second mixer, driven by a phase shifted copy of the first pump tone, recombines and disentangles the two beams. We show that interference fringes of the intensity of the final output noise, referred to the input of the second mixer, pass under the level of vacuum for a range of phase shifts. The minimal measured noise intensity provides a quantitative measure of entanglement and yields a lower bound of 6 Mebits/s on the rate of entangled bits produced by the first mixer.
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http://arxiv.org/abs/1204.0732
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