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Proceedings Paper

Quantum information processing with Schrödinger cats
Author(s): Kae Nemoto; Alexei Gilchrist; William J. Munro; Tim C. Ralph; Samuel L. Braunstein; Gerard J. Milburn
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Paper Abstract

Quantum optics has proved a fertile field for experimental tests of quantum information science, from experimental verification of the violation of the Bell inequalities to quantum teleportation. However it was long believed that quantum optics would not provide a practical path to efficient and scaleable quantum computation, and most current efforts to achieve a scaleable quantum computer have focussed on solid state implementations. This orthodoxy was challenged recently when Knill et al. showed that given single photon sources and single photon detectors, linear optics alone would suffice to implement efficient quantum computation. While this result is surprising, the complexity of the optical networks required is daunting. In this talk we propose an efficient scheme which is elegant in its simplicity. We indicate how fundamental single and two qubit gates can be achieved. By encoding the quantum information in multi-photon coherent states, rather than single photon states, simple optical manipulations acquire unexpected power. As an application of this new information processing ability we investigate a class of high precision measurements. We show how superpositions of coherent states allow displacement measurements at the Heisenberg limit. Entangling many superpositions of coherent states offers a significant advantage over a single mode superposition states with the same mean photon number.

Paper Details

Date Published: 16 May 2003
PDF: 10 pages
Proc. SPIE 5111, Fluctuations and Noise in Photonics and Quantum Optics, (16 May 2003); doi: 10.1117/12.497230
Show Author Affiliations
Kae Nemoto, Univ. of Wales (United Kingdom)
Hewlett-Packard Labs. (United Kingdom)
Alexei Gilchrist, Univ. of Queensland (Australia)
William J. Munro, Hewlett-Packard Labs. (United Kingdom)
Tim C. Ralph, Univ. of Queensland (Australia)
Samuel L. Braunstein, Univ. of Wales (United Kingdom)
Gerard J. Milburn, Univ. of Queensland (Australia)

Published in SPIE Proceedings Vol. 5111:
Fluctuations and Noise in Photonics and Quantum Optics
Derek Abbott; Jeffrey H. Shapiro; Yoshihisa Yamamoto, Editor(s)

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