Continuous-variable entanglement purification with atomic systems

We present a proposal for entanglement purification of the continuous-variable quantum state of two propagating optical fields. The scheme is based on letting each field interact with a local node, an atomic ensemble, whose internal collective excitation plays the role of an ancillary continuous variable resource. Entanglement purification is achieved by a dichotomic measurement, representing the required non-Gaussian element, and which consists in detecting the presence or absence of collective excitations in the atomic ensemble. This scheme can be extended to networks, where the nodes are single trapped atoms, and constitutes an important building block for the implementation of a continuous-variable quantum repeater.Comment: Published in Feature Issue "Quantum Optical Information Technologies

A proposal for the implementation of a quantum phase gate in a five-level atomic medium

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A proposal for the implementation of a quantum phase gate in a five-level atomic medium

10 page(s

Memory-enhanced noiseless cross-phase modulation

Large nonlinearity at the single-photon level can pave the way for the implementation of universal quantum gates. However, realizing large and noiseless nonlinearity at such low light levels has been a great challenge for scientists in the past decade. H