Abstract

We present a bright, narrowband, portable, quasi-phase-matched two-crystal source generating polarization-entangled photon pairs at 809 nm and 1555 nm at a maximum rate of 1.2 × 106 s-1 THz-1 mW-1 after coupling to single-mode fiber. The quantum channel at 1555 nm and the synchronization signal gating the single photon detector are multiplexed in the same optical fiber of length 27 km by means of wavelength division multiplexers (WDM) having 100 GHz (0.8 nm) spacing between channels. This implementation makes quantum communication applications compatible with current high-speed optical networks.

© 2007 Optical Society of America

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  1. N.  Gisin, G.  Ribordy, W.  Tittel, and H.  Zbinden, "Quantum cryptography," Rev. Mod. Phys.  74, 145-195 (2001).
    [CrossRef]
  2. A.K. Ekert, "Quantum cryptography based on Bell’s theorem," Phys. Rev. Lett. 67, 661 (1991).
    [CrossRef] [PubMed]
  3. I. Marcikic, H. de Riedmatten, W. Tittel, H. Zbinden, and N. Gisin, "Long-distance teleportation of qubits at telecommunication wavelengths," Nature 421, 509-513 (2003).
    [CrossRef] [PubMed]
  4. H.  Briegel, W.  Dür, J. I.  Cirac and P.  Zoller, "Quantum repeaters: the role of imperfect local operations in quantum communication," Phys. Rev. Lett.  81, 5932-5935 (1998).
    [CrossRef]
  5. P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A. V.  Sergienko, and Y. H.  Shih, "New High-Intensity Source of Polarization-Entangled Photon Pairs," Phys. Rev. Lett.  75, 4337-4340 (1995).
    [CrossRef] [PubMed]
  6. C. E. Kuklewicz, M. Fiorentino, G. Messin, F. N. C. Wong, and J. H. Shapiro, "High-flux source of polarization entangled photons from a periodically-poled KTiOPO4 parametric downconverter," Phys. Rev. A 69, 013807 (2004).
    [CrossRef]
  7. S. Tanzilli, H. De Riedmatten, W. Tittel, H. Zbinden, P. Baldi, M. De Micheli, D. B. Ostrowsky, and N. Gisin, "Highly efficient photon-pair source using a periodically poled lithium niobate waveguide," Electron. Lett. 37, 26-28 (2001).
    [CrossRef]
  8. M. Pelton, P. Marsden, D. Ljunggren, M. Tengner, A. Karlsson, A. Fragemann, C. Canalias, and F. Laurell, "Bright, single-spatial-mode source of frequency non-degenerate, polarization-entangled photon pairs using periodically poled KTP," Opt. Express 12, 3573-3580 (2004).
    [CrossRef] [PubMed]
  9. D. Ljunggren, M. Tengner, P. Marsden, and M. Pelton, "Theory and experiment of entanglement in a quasi-phase-matched two-crystal source," Phys. Rev. A 73, 032326 (2006).
    [CrossRef]
  10. D. Ljunggren and M. Tengner, "Optimal focusing for maximal collection of entangled narrow-band photon pairs into single-mode fibers," Phys. Rev. A 72, 062301 (2005).
    [CrossRef]
  11. C.  Liang, K. F.  Lee, J.  Chen, and P.  Kumar, "Distribution of fiber-generated polarization entangled photon-pairs over 100 km of standard fiber in OC-192 WDM environment," postdeadline paper, Optical Fiber Communications Conference (OFC’2006), paper PDP35.
  12. H. Hübel, M. R. Vanner, T. Lederer, B. Blauensteiner, A. Poppe, and A. Zeilinger, "High-fidelity transmission of polarization entangled qubits over 100 km of telecom fibers," Opt. Express 15, 7853-7862 (2007).
    [CrossRef] [PubMed]
  13. P.W. Shor and J. Preskill, "Simple proof of security of the BB84 Quantum key distribution protocol," Phys. Rev. Lett. 85, 441-444 (2000).
    [CrossRef] [PubMed]
  14. J. J. Xia, D. Z. Chen, G. Wellbrock, A. Zavriyev, A. C. Beal, and K. M. Lee, "In-band quantum key distribution (QKD) on fiber populated by high-speed classical data channels," Optical Fiber Communications Conference (OFC’2006), paper OTuJ7.
  15. M. Fiorentino, G. Messin, C. E. Kuklewicz, F. N. C. Wong, and J. H. Shapiro, "Generation of ultrabright tunable polarization entanglement without spatial, spectral, or temporal constraints," Phys. Rev. A 69, 041801 (2004).
    [CrossRef]

2006 (1)

D. Ljunggren, M. Tengner, P. Marsden, and M. Pelton, "Theory and experiment of entanglement in a quasi-phase-matched two-crystal source," Phys. Rev. A 73, 032326 (2006).
[CrossRef]

2005 (1)

D. Ljunggren and M. Tengner, "Optimal focusing for maximal collection of entangled narrow-band photon pairs into single-mode fibers," Phys. Rev. A 72, 062301 (2005).
[CrossRef]

2004 (3)

C. E. Kuklewicz, M. Fiorentino, G. Messin, F. N. C. Wong, and J. H. Shapiro, "High-flux source of polarization entangled photons from a periodically-poled KTiOPO4 parametric downconverter," Phys. Rev. A 69, 013807 (2004).
[CrossRef]

M. Fiorentino, G. Messin, C. E. Kuklewicz, F. N. C. Wong, and J. H. Shapiro, "Generation of ultrabright tunable polarization entanglement without spatial, spectral, or temporal constraints," Phys. Rev. A 69, 041801 (2004).
[CrossRef]

M. Pelton, P. Marsden, D. Ljunggren, M. Tengner, A. Karlsson, A. Fragemann, C. Canalias, and F. Laurell, "Bright, single-spatial-mode source of frequency non-degenerate, polarization-entangled photon pairs using periodically poled KTP," Opt. Express 12, 3573-3580 (2004).
[CrossRef] [PubMed]

2003 (1)

I. Marcikic, H. de Riedmatten, W. Tittel, H. Zbinden, and N. Gisin, "Long-distance teleportation of qubits at telecommunication wavelengths," Nature 421, 509-513 (2003).
[CrossRef] [PubMed]

2001 (2)

N.  Gisin, G.  Ribordy, W.  Tittel, and H.  Zbinden, "Quantum cryptography," Rev. Mod. Phys.  74, 145-195 (2001).
[CrossRef]

S. Tanzilli, H. De Riedmatten, W. Tittel, H. Zbinden, P. Baldi, M. De Micheli, D. B. Ostrowsky, and N. Gisin, "Highly efficient photon-pair source using a periodically poled lithium niobate waveguide," Electron. Lett. 37, 26-28 (2001).
[CrossRef]

2000 (2)

1998 (1)

H.  Briegel, W.  Dür, J. I.  Cirac and P.  Zoller, "Quantum repeaters: the role of imperfect local operations in quantum communication," Phys. Rev. Lett.  81, 5932-5935 (1998).
[CrossRef]

1995 (1)

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A. V.  Sergienko, and Y. H.  Shih, "New High-Intensity Source of Polarization-Entangled Photon Pairs," Phys. Rev. Lett.  75, 4337-4340 (1995).
[CrossRef] [PubMed]

1991 (1)

A.K. Ekert, "Quantum cryptography based on Bell’s theorem," Phys. Rev. Lett. 67, 661 (1991).
[CrossRef] [PubMed]

Baldi, P.

S. Tanzilli, H. De Riedmatten, W. Tittel, H. Zbinden, P. Baldi, M. De Micheli, D. B. Ostrowsky, and N. Gisin, "Highly efficient photon-pair source using a periodically poled lithium niobate waveguide," Electron. Lett. 37, 26-28 (2001).
[CrossRef]

Blauensteiner, B.

Briegel, H.

H.  Briegel, W.  Dür, J. I.  Cirac and P.  Zoller, "Quantum repeaters: the role of imperfect local operations in quantum communication," Phys. Rev. Lett.  81, 5932-5935 (1998).
[CrossRef]

Canalias, C.

Cirac, J. I.

H.  Briegel, W.  Dür, J. I.  Cirac and P.  Zoller, "Quantum repeaters: the role of imperfect local operations in quantum communication," Phys. Rev. Lett.  81, 5932-5935 (1998).
[CrossRef]

De Micheli, M.

S. Tanzilli, H. De Riedmatten, W. Tittel, H. Zbinden, P. Baldi, M. De Micheli, D. B. Ostrowsky, and N. Gisin, "Highly efficient photon-pair source using a periodically poled lithium niobate waveguide," Electron. Lett. 37, 26-28 (2001).
[CrossRef]

de Riedmatten, H.

I. Marcikic, H. de Riedmatten, W. Tittel, H. Zbinden, and N. Gisin, "Long-distance teleportation of qubits at telecommunication wavelengths," Nature 421, 509-513 (2003).
[CrossRef] [PubMed]

S. Tanzilli, H. De Riedmatten, W. Tittel, H. Zbinden, P. Baldi, M. De Micheli, D. B. Ostrowsky, and N. Gisin, "Highly efficient photon-pair source using a periodically poled lithium niobate waveguide," Electron. Lett. 37, 26-28 (2001).
[CrossRef]

Dür, W.

H.  Briegel, W.  Dür, J. I.  Cirac and P.  Zoller, "Quantum repeaters: the role of imperfect local operations in quantum communication," Phys. Rev. Lett.  81, 5932-5935 (1998).
[CrossRef]

Ekert, A.K.

A.K. Ekert, "Quantum cryptography based on Bell’s theorem," Phys. Rev. Lett. 67, 661 (1991).
[CrossRef] [PubMed]

Fiorentino, M.

M. Fiorentino, G. Messin, C. E. Kuklewicz, F. N. C. Wong, and J. H. Shapiro, "Generation of ultrabright tunable polarization entanglement without spatial, spectral, or temporal constraints," Phys. Rev. A 69, 041801 (2004).
[CrossRef]

C. E. Kuklewicz, M. Fiorentino, G. Messin, F. N. C. Wong, and J. H. Shapiro, "High-flux source of polarization entangled photons from a periodically-poled KTiOPO4 parametric downconverter," Phys. Rev. A 69, 013807 (2004).
[CrossRef]

Fragemann, A.

Gisin, N.

I. Marcikic, H. de Riedmatten, W. Tittel, H. Zbinden, and N. Gisin, "Long-distance teleportation of qubits at telecommunication wavelengths," Nature 421, 509-513 (2003).
[CrossRef] [PubMed]

N.  Gisin, G.  Ribordy, W.  Tittel, and H.  Zbinden, "Quantum cryptography," Rev. Mod. Phys.  74, 145-195 (2001).
[CrossRef]

S. Tanzilli, H. De Riedmatten, W. Tittel, H. Zbinden, P. Baldi, M. De Micheli, D. B. Ostrowsky, and N. Gisin, "Highly efficient photon-pair source using a periodically poled lithium niobate waveguide," Electron. Lett. 37, 26-28 (2001).
[CrossRef]

Hübel, H.

Karlsson, A.

Kuklewicz, C. E.

M. Fiorentino, G. Messin, C. E. Kuklewicz, F. N. C. Wong, and J. H. Shapiro, "Generation of ultrabright tunable polarization entanglement without spatial, spectral, or temporal constraints," Phys. Rev. A 69, 041801 (2004).
[CrossRef]

C. E. Kuklewicz, M. Fiorentino, G. Messin, F. N. C. Wong, and J. H. Shapiro, "High-flux source of polarization entangled photons from a periodically-poled KTiOPO4 parametric downconverter," Phys. Rev. A 69, 013807 (2004).
[CrossRef]

Kwiat, P. G.

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A. V.  Sergienko, and Y. H.  Shih, "New High-Intensity Source of Polarization-Entangled Photon Pairs," Phys. Rev. Lett.  75, 4337-4340 (1995).
[CrossRef] [PubMed]

Laurell, F.

Lederer, T.

Ljunggren, D.

D. Ljunggren, M. Tengner, P. Marsden, and M. Pelton, "Theory and experiment of entanglement in a quasi-phase-matched two-crystal source," Phys. Rev. A 73, 032326 (2006).
[CrossRef]

D. Ljunggren and M. Tengner, "Optimal focusing for maximal collection of entangled narrow-band photon pairs into single-mode fibers," Phys. Rev. A 72, 062301 (2005).
[CrossRef]

M. Pelton, P. Marsden, D. Ljunggren, M. Tengner, A. Karlsson, A. Fragemann, C. Canalias, and F. Laurell, "Bright, single-spatial-mode source of frequency non-degenerate, polarization-entangled photon pairs using periodically poled KTP," Opt. Express 12, 3573-3580 (2004).
[CrossRef] [PubMed]

Marcikic, I.

I. Marcikic, H. de Riedmatten, W. Tittel, H. Zbinden, and N. Gisin, "Long-distance teleportation of qubits at telecommunication wavelengths," Nature 421, 509-513 (2003).
[CrossRef] [PubMed]

Marsden, P.

Mattle, K.

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A. V.  Sergienko, and Y. H.  Shih, "New High-Intensity Source of Polarization-Entangled Photon Pairs," Phys. Rev. Lett.  75, 4337-4340 (1995).
[CrossRef] [PubMed]

Messin, G.

C. E. Kuklewicz, M. Fiorentino, G. Messin, F. N. C. Wong, and J. H. Shapiro, "High-flux source of polarization entangled photons from a periodically-poled KTiOPO4 parametric downconverter," Phys. Rev. A 69, 013807 (2004).
[CrossRef]

M. Fiorentino, G. Messin, C. E. Kuklewicz, F. N. C. Wong, and J. H. Shapiro, "Generation of ultrabright tunable polarization entanglement without spatial, spectral, or temporal constraints," Phys. Rev. A 69, 041801 (2004).
[CrossRef]

Ostrowsky, D. B.

S. Tanzilli, H. De Riedmatten, W. Tittel, H. Zbinden, P. Baldi, M. De Micheli, D. B. Ostrowsky, and N. Gisin, "Highly efficient photon-pair source using a periodically poled lithium niobate waveguide," Electron. Lett. 37, 26-28 (2001).
[CrossRef]

Pelton, M.

Poppe, A.

Preskill, J.

P.W. Shor and J. Preskill, "Simple proof of security of the BB84 Quantum key distribution protocol," Phys. Rev. Lett. 85, 441-444 (2000).
[CrossRef] [PubMed]

Ribordy, G.

N.  Gisin, G.  Ribordy, W.  Tittel, and H.  Zbinden, "Quantum cryptography," Rev. Mod. Phys.  74, 145-195 (2001).
[CrossRef]

Sergienko, A. V.

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A. V.  Sergienko, and Y. H.  Shih, "New High-Intensity Source of Polarization-Entangled Photon Pairs," Phys. Rev. Lett.  75, 4337-4340 (1995).
[CrossRef] [PubMed]

Shapiro, J. H.

M. Fiorentino, G. Messin, C. E. Kuklewicz, F. N. C. Wong, and J. H. Shapiro, "Generation of ultrabright tunable polarization entanglement without spatial, spectral, or temporal constraints," Phys. Rev. A 69, 041801 (2004).
[CrossRef]

C. E. Kuklewicz, M. Fiorentino, G. Messin, F. N. C. Wong, and J. H. Shapiro, "High-flux source of polarization entangled photons from a periodically-poled KTiOPO4 parametric downconverter," Phys. Rev. A 69, 013807 (2004).
[CrossRef]

Shih, Y. H.

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A. V.  Sergienko, and Y. H.  Shih, "New High-Intensity Source of Polarization-Entangled Photon Pairs," Phys. Rev. Lett.  75, 4337-4340 (1995).
[CrossRef] [PubMed]

Shor, P.W.

P.W. Shor and J. Preskill, "Simple proof of security of the BB84 Quantum key distribution protocol," Phys. Rev. Lett. 85, 441-444 (2000).
[CrossRef] [PubMed]

Tanzilli, S.

S. Tanzilli, H. De Riedmatten, W. Tittel, H. Zbinden, P. Baldi, M. De Micheli, D. B. Ostrowsky, and N. Gisin, "Highly efficient photon-pair source using a periodically poled lithium niobate waveguide," Electron. Lett. 37, 26-28 (2001).
[CrossRef]

Tengner, M.

D. Ljunggren, M. Tengner, P. Marsden, and M. Pelton, "Theory and experiment of entanglement in a quasi-phase-matched two-crystal source," Phys. Rev. A 73, 032326 (2006).
[CrossRef]

D. Ljunggren and M. Tengner, "Optimal focusing for maximal collection of entangled narrow-band photon pairs into single-mode fibers," Phys. Rev. A 72, 062301 (2005).
[CrossRef]

M. Pelton, P. Marsden, D. Ljunggren, M. Tengner, A. Karlsson, A. Fragemann, C. Canalias, and F. Laurell, "Bright, single-spatial-mode source of frequency non-degenerate, polarization-entangled photon pairs using periodically poled KTP," Opt. Express 12, 3573-3580 (2004).
[CrossRef] [PubMed]

Tittel, W.

I. Marcikic, H. de Riedmatten, W. Tittel, H. Zbinden, and N. Gisin, "Long-distance teleportation of qubits at telecommunication wavelengths," Nature 421, 509-513 (2003).
[CrossRef] [PubMed]

N.  Gisin, G.  Ribordy, W.  Tittel, and H.  Zbinden, "Quantum cryptography," Rev. Mod. Phys.  74, 145-195 (2001).
[CrossRef]

S. Tanzilli, H. De Riedmatten, W. Tittel, H. Zbinden, P. Baldi, M. De Micheli, D. B. Ostrowsky, and N. Gisin, "Highly efficient photon-pair source using a periodically poled lithium niobate waveguide," Electron. Lett. 37, 26-28 (2001).
[CrossRef]

Vanner, M. R.

Weinfurter, H.

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A. V.  Sergienko, and Y. H.  Shih, "New High-Intensity Source of Polarization-Entangled Photon Pairs," Phys. Rev. Lett.  75, 4337-4340 (1995).
[CrossRef] [PubMed]

Wong, F. N. C.

C. E. Kuklewicz, M. Fiorentino, G. Messin, F. N. C. Wong, and J. H. Shapiro, "High-flux source of polarization entangled photons from a periodically-poled KTiOPO4 parametric downconverter," Phys. Rev. A 69, 013807 (2004).
[CrossRef]

M. Fiorentino, G. Messin, C. E. Kuklewicz, F. N. C. Wong, and J. H. Shapiro, "Generation of ultrabright tunable polarization entanglement without spatial, spectral, or temporal constraints," Phys. Rev. A 69, 041801 (2004).
[CrossRef]

Zbinden, H.

I. Marcikic, H. de Riedmatten, W. Tittel, H. Zbinden, and N. Gisin, "Long-distance teleportation of qubits at telecommunication wavelengths," Nature 421, 509-513 (2003).
[CrossRef] [PubMed]

N.  Gisin, G.  Ribordy, W.  Tittel, and H.  Zbinden, "Quantum cryptography," Rev. Mod. Phys.  74, 145-195 (2001).
[CrossRef]

S. Tanzilli, H. De Riedmatten, W. Tittel, H. Zbinden, P. Baldi, M. De Micheli, D. B. Ostrowsky, and N. Gisin, "Highly efficient photon-pair source using a periodically poled lithium niobate waveguide," Electron. Lett. 37, 26-28 (2001).
[CrossRef]

Zeilinger, A.

H. Hübel, M. R. Vanner, T. Lederer, B. Blauensteiner, A. Poppe, and A. Zeilinger, "High-fidelity transmission of polarization entangled qubits over 100 km of telecom fibers," Opt. Express 15, 7853-7862 (2007).
[CrossRef] [PubMed]

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A. V.  Sergienko, and Y. H.  Shih, "New High-Intensity Source of Polarization-Entangled Photon Pairs," Phys. Rev. Lett.  75, 4337-4340 (1995).
[CrossRef] [PubMed]

Zoller, P.

H.  Briegel, W.  Dür, J. I.  Cirac and P.  Zoller, "Quantum repeaters: the role of imperfect local operations in quantum communication," Phys. Rev. Lett.  81, 5932-5935 (1998).
[CrossRef]

Electron. Lett. (1)

S. Tanzilli, H. De Riedmatten, W. Tittel, H. Zbinden, P. Baldi, M. De Micheli, D. B. Ostrowsky, and N. Gisin, "Highly efficient photon-pair source using a periodically poled lithium niobate waveguide," Electron. Lett. 37, 26-28 (2001).
[CrossRef]

Nature (1)

I. Marcikic, H. de Riedmatten, W. Tittel, H. Zbinden, and N. Gisin, "Long-distance teleportation of qubits at telecommunication wavelengths," Nature 421, 509-513 (2003).
[CrossRef] [PubMed]

Opt. Express (2)

Phys. Rev. A (4)

C. E. Kuklewicz, M. Fiorentino, G. Messin, F. N. C. Wong, and J. H. Shapiro, "High-flux source of polarization entangled photons from a periodically-poled KTiOPO4 parametric downconverter," Phys. Rev. A 69, 013807 (2004).
[CrossRef]

M. Fiorentino, G. Messin, C. E. Kuklewicz, F. N. C. Wong, and J. H. Shapiro, "Generation of ultrabright tunable polarization entanglement without spatial, spectral, or temporal constraints," Phys. Rev. A 69, 041801 (2004).
[CrossRef]

D. Ljunggren, M. Tengner, P. Marsden, and M. Pelton, "Theory and experiment of entanglement in a quasi-phase-matched two-crystal source," Phys. Rev. A 73, 032326 (2006).
[CrossRef]

D. Ljunggren and M. Tengner, "Optimal focusing for maximal collection of entangled narrow-band photon pairs into single-mode fibers," Phys. Rev. A 72, 062301 (2005).
[CrossRef]

Phys. Rev. Lett. (4)

H.  Briegel, W.  Dür, J. I.  Cirac and P.  Zoller, "Quantum repeaters: the role of imperfect local operations in quantum communication," Phys. Rev. Lett.  81, 5932-5935 (1998).
[CrossRef]

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A. V.  Sergienko, and Y. H.  Shih, "New High-Intensity Source of Polarization-Entangled Photon Pairs," Phys. Rev. Lett.  75, 4337-4340 (1995).
[CrossRef] [PubMed]

A.K. Ekert, "Quantum cryptography based on Bell’s theorem," Phys. Rev. Lett. 67, 661 (1991).
[CrossRef] [PubMed]

P.W. Shor and J. Preskill, "Simple proof of security of the BB84 Quantum key distribution protocol," Phys. Rev. Lett. 85, 441-444 (2000).
[CrossRef] [PubMed]

Rev. Mod. Phys. (1)

N.  Gisin, G.  Ribordy, W.  Tittel, and H.  Zbinden, "Quantum cryptography," Rev. Mod. Phys.  74, 145-195 (2001).
[CrossRef]

Other (2)

C.  Liang, K. F.  Lee, J.  Chen, and P.  Kumar, "Distribution of fiber-generated polarization entangled photon-pairs over 100 km of standard fiber in OC-192 WDM environment," postdeadline paper, Optical Fiber Communications Conference (OFC’2006), paper PDP35.

J. J. Xia, D. Z. Chen, G. Wellbrock, A. Zavriyev, A. C. Beal, and K. M. Lee, "In-band quantum key distribution (QKD) on fiber populated by high-speed classical data channels," Optical Fiber Communications Conference (OFC’2006), paper OTuJ7.

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Figures (4)

Fig. 1.
Fig. 1.

Experimental setup. ALICE. Pump arm. LASER, 532 nm 50 mW pump laser; BPF, band-pass filter; HWP, half-wave plate; Lp, pump focusing lens (fp = 150 mm); BSF, 532 nm band-stop filter; DM, dichroic mirror. Signal arm. Ls, collimating lens for signal (fs = 200 mm); LPF, long-pass filter (Schott RG715); BS, 50/50 beam-splitter; PBS, polarizing beam-splitter; SMF, single-mode fiber coupler; APD, Si avalanche photo-detector; DEL, delay generator; DFB, distributed-feedback (trigger) laser at 1555.75 nm; CRC, circulator; FBG, Fiber Bragg grating. Idler arm. Li, collimating lens for idler (fi = 150 mm); LPF, long-pass filter (Schott RG1000); CLC, calcite; PMF, polarization-maintaining fiber (3 meter-long). WDM, wavelength division multiplexer. BOB. Synchronization channel. PD, 1GHz InGaAs fiber optic photo-detector; TDC, time-discriminator-circuit; CNT, counter. Quantum channel. PC, fiber coupled polarization controller. APD, InGaAs avalanche photo-detector. Dashed lines, free-space; black lines, single-mode fiber; grey line, BNC cable. We use external (electronic) triggering (with a BNC cable connecting both single-photon detectors) when measuring the performances of the source without the 27 km fiber link.

Fig. 2.
Fig. 2.

1555 nm spectrum for horizontal polarization without conditional gating at 809 nm. FWHM is about 0.5 nm. The background of 0.05 pW is coming from the noise of the detection system in the spectrograph (model Agilent 86140B).

Fig. 3.
Fig. 3.

Coincidence rate after 100 m of fiber as a function of idler polarization for each of the 4 polarization states (H/V and D/A) of the signal.

Fig. 4.
Fig. 4.

Coincidence rate after 27 km of fiber as a function of idler polarization for each of the 4 polarization states (H/V and D/A) of the signal.

Equations (1)

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Φ φ > = 1 2 ( V ( ω s ) V ( ω i ) > + e H ( ω s ) H ( ω i ) > ) , ω i + ω s = ω p ,

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