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Phys. Rev. Lett. 98, 203602 (2007) [4 pages]

Entanglement Generation by Fock-State Filtration

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K. J. Resch1,2, J. L. O’Brien1,3, T. J. Weinhold1, K. Sanaka4, B. P. Lanyon1, N. K. Langford1, and A. G. White1
1Department of Physics & Centre for Quantum Computer Technology, University of Queensland, Brisbane, QLD 4072, Australia
2Department of Physics & Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada
3H. H. Wills Physics Laboratory & Department of Electrical and Electronic Engineering, University of Bristol, Bristol, BS8 1UB, United Kingdom
4E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305, USA

Received 31 July 2006; published 16 May 2007

We demonstrate a Fock-state filter which is capable of preferentially blocking single photons over photon pairs. The large conditional nonlinearities are based on higher-order quantum interference, using linear optics, an ancilla photon, and measurement. We demonstrate that the filter acts coherently by using it to convert unentangled photon pairs to a path-entangled state. We quantify the degree of entanglement by transforming the path information to polarization information; applying quantum state tomography we measure a tangle of T=(20±9)%.

© 2007 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.98.203602
DOI:
10.1103/PhysRevLett.98.203602
PACS:
42.50.Dv, 03.65.Wj, 03.67.Mn, 42.50.Nn
 
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