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arXiv:quant-ph/9912017 · Physical Review Letters

Entanglement Purification of Gaussian Continuous Variable Quantum States

L.-M. Duan, G. Giedke, J. I. Cirac, P. Zoller

Published Apr 24, 2000• 196 citations
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Abstract

We describe an entanglement purification protocol to generate maximally entangled states with high efficiencies from two-mode squeezed states or from mixed Gaussian continuous entangled states. The protocol relies on a local quantum nondemolition measurement of the total excitation number of several continuous variable entangled pairs. We propose an optical scheme to do this kind of measurement using cavity enhanced cross-Kerr interactions.

DOI
10.1103/physrevlett.84.4002

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We describe an entanglement purification protocol to generate maximally entangled states with high efficiencies from two-mode squeezed states or from mixed Gaussian continuous entangled states. The protocol relies on a local quantum nondemolition measurement of the total excitation number of several continuous variable entangled pairs. We propose an optical scheme to do this kind of measurement using cavity enhanced cross-Kerr interactions.
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We present a proposal for entanglement purification of the continuous-variable quantum state of two propagating optical fields. The scheme is based on each field interacting with a local node-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, which consists of 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.
We present an entanglement purification protocol for photonic mixed entangled states based on the two-mode polarization nondemolition parity detectors. Without the use of the controlled-NOT (CNOT) operations, the efficiency of our protocol can nearly approach that of the CNOT protocol. The total successful probability of our protocol can be nearly enhanced to the quantity twice as large as that of the linear-optics-based protocol. Besides, our protocol adopts common photon detectors rather than the sophisticated single-photon detectors required in the linear-optics-based protocol.