Pulsed Sagnac source of narrow-band polarization-entangled photons

Onur Kuzucu and Franco N. C. Wong
Phys. Rev. A 77, 032314 – Published 7 March 2008

Abstract

We demonstrate pulsed operation of a bidirectionally pumped polarization Sagnac interferometric down-conversion source and its generation of narrow-band, high-visibility polarization-entangled photons. Driven by a narrow-band, mode-locked pump at 390.35 nm, the phase-stable Sagnac source with a type-II phase-matched periodically poled KTiOPO4 crystal is capable of producing 0.01 entangled pair per pulse in a 0.15-nm bandwidth centered at 780.7 nm with 1 mW of average pump power at a repetition rate of 31.1 MHz. We have achieved a mean photon-pair generation rate of as high as 0.7 pair per pulse, at which multipair events dominate and significantly reduce the two-photon quantum-interference visibility. For low generation probability α, the reduced visibility V=1α is independent of the throughput efficiency and of the polarization analysis basis, which can be utilized to yield an accurate estimate of the generation rate α. At low α we have characterized the source entanglement quality in three different ways: average quantum-interference visibility of 99%, the Clauser-Horne-Shimony-Holt S parameter of 2.739±0.119, and quantum state tomography with 98.85% singlet-state fidelity. The narrow-band pulsed Sagnac source of entangled photons is suitable for use in quantum information processing applications such as free-space quantum key distribution.

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  • Received 29 October 2007

DOI:https://doi.org/10.1103/PhysRevA.77.032314

©2008 American Physical Society

Authors & Affiliations

Onur Kuzucu and Franco N. C. Wong

  • Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

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Issue

Vol. 77, Iss. 3 — March 2008

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