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AIP conference proceedings

A Four-Photon Entangled State for Linear Optical Quantum Information Processing

Yuuki Tokunaga

Published Jan 1, 2004• 0 citations
Publisher

Abstract

We propose a simple experimental scheme for preparing a four‐photon polarization entangled state which plays important roles for quantum information processing. By using the four‐photon entangled state, we also present a scheme of a controlled‐NOT gate through teleportation, in which both path and polarization freedoms of photons are utilized. These schemes are constructed with four photons from parametric down‐conversion, linear optical devices, and conventional photon detectors, all of which are available in current technology.

DOI
10.1063/1.1834451

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We propose a simple experimental scheme for preparing a four‐photon polarization entangled state which plays important roles for quantum information processing. By using the four‐photon entangled state, we also present a scheme of a controlled‐NOT gate through teleportation, in which both path and polarization freedoms of photons are utilized. These schemes are constructed with four photons from parametric down‐conversion, linear optical devices, and conventional photon detectors, all of which are available in current technology.
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We propose two interesting methods of generating the four-photon W state. These methods use parametric down-conversion processes, linear optical elements, and commercial photon detectors, which are readily feasible under current technology. They can also be used to generate the three-photon W state, the three-photon Greenberger–Horne–Zeilinger state, and the three-photon maximally entangled photon-number state (a typical photon-number entanglement state) by simply changing some experimental components or their parameters. Moreover, assuming we have photon number-resolving detectors, these methods can develop into methods that generate a general n -photon W state. They are expected to become powerful tools for experimental investigations of multipartite entanglement and its applications to quantum information processing.
Abstract We propose a theoretical protocol for preparing four-photon polarization entangled decoherence-free states, which are immune to the collective noise. With the assistance of the cross-Kerr nonlinearities, a two-photon spatial entanglement gate, two controlled-NOT gates, a four-photon polarization entanglement gate are inserted into the circuit, where X homodyne measurements are aptly applied. Combined with some swap gates and simple linear optical elements, four-photon polarization entangled decoherence-free states which can be utilized to represent two logical qubits, |0〉L and |1〉L are achieved at the output ports of the circuit. This generation scheme may be implemented with current experimental techniques.