Abstract

We have distributed entangled photons directly through the atmosphere to a receiver station 7.8 km away over the city of Vienna, Austria at night. Detection of one photon from our entangled pairs constitutes a triggered single photon source from the sender. With no direct time-stable connection, the two stations found coincidence counts in the detection events by calculating the cross-correlation of locally-recorded time stamps shared over a public internet channel. For this experiment, our quantum channel was maintained for a total of 40 minutes during which time a coincidence lock found approximately 60000 coincident detection events. The polarization correlations in those events yielded a Bell parameter, S=2.27±0.019, which violates the CHSH-Bell inequality by 14 standard deviations. This result is promising for entanglement-based free-space quantum communication in high-density urban areas. It is also encouraging for optical quantum communication between ground stations and satellites since the length of our free-space link exceeds the atmospheric equivalent.

© 2005 Optical Society of America

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    [CrossRef] [PubMed]
  5. I.  Marcikic, H.  de Riedmatten, W.  Tittel, H.  Zbinden, N.  Gisin, “Long-distance teleportation of qubits at telecommunication wavelengths,” Nature 421, 509–513 (2003).
    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef] [PubMed]
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    [CrossRef]
  13. J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, “Secure free-space key exchange to 1.9 km and beyond,” J. Mod. Opt. 48, 1887–1901 (2001).
  14. C.  Kurtsiefer, P.  Zarda, M.  Halder, H.  Weinfurter, P.M.  Gorman, P.R.  Tapster, J.G.  Rarity, “A step towards global key distribution,” Nature 419, 450 (2002).
    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef]
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  18. J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, P.  Knight, “Ground to satellite secure key exchange using quantum cryptography,” New J. Phys. 4, 82, (2002).
    [CrossRef]
  19. J.E.  Nordholt, R.J.  Hughes, G.L.  Morgan, C.G.  Peterson, C.C.  Wipf, “Present and future quantum key distribution”, Proc. SPIE 4635, 116–126 (2002).
    [CrossRef]
  20. M.  Aspelmeyer, T.  Jennewein, M.  Pfenningbauer, W.R.  Leeb, A.  Zeilinger, “Long-distance quantum communication with entangled photons using satellites,” IEEE J. Sel. Top. Quantum Electron. 9, 1541–1551 (2003).
    [CrossRef]
  21. C.F.  Bohren, B.A.  Albrecht, Atmospheric Thermodynamics, (Oxford University Press, New York,1988).
  22. The transmission of 800nm light from the whole vertical atmosphere is about 80% under good weather conditions [18,19]. The horizontal attenuation coefficient measured in Vienna was approximately ?=0.05km-1. The horizontal distance with the same attenuation as the whole atmosphere vertically is, L=-ln(0.8)/?=4.5km. H.  Horwath, L.  Alados Arboledas, F.J.  Olmo, O.  Jovanovi?, M.  Gangl, W.  Kaller, C.  Sánchez, H.  Sauerzopf, S.  Seidl, “Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing,” Journal of Geophysical Research (Atmospheres) 107, No. D19, AAC 9 (2002).
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    [CrossRef]
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    [CrossRef] [PubMed]
  25. S.F.  Seward, P.R.  Tapster, J.G.  Walker, J.G.  Rarity, “Daylight demonstration of low-light-level communication system using correlated photon pairs,” Quantum Opt. 3, 201–207 (1991).
    [CrossRef]
  26. C. K.  Hong, L.  Mandel, “Experimental realization of a localized one-photon state,” Phys. Rev. Lett. 56, 58–60 (1986).
    [CrossRef] [PubMed]
  27. J.  Bell, “On the Einstein-Podolsky-Rosen Paradox,” Physics 1, 195–200 (1964).
  28. J.F.  Clauser, M.A.  Horne, A.  Shimony, R.  Holt, “Proposed experiment to test local hidden-variable theories,” Phys. Rev. Lett. 23, 880–884 (1969).
    [CrossRef]
  29. P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A.V.  Sergienko, Y.  Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).
    [CrossRef] [PubMed]
  30. N.  Gisin, G.  Ribordy, W.  Tittel, H.  Zbinden, “Quantum Cryptography,” Rev. Mod. Phys. 74, 145–195 (2002).
    [CrossRef]
  31. N.  Lütkenhaus, “Estimates for practical quantum cryptography,” Phys. Rev. A 59, 3301–3319 (1999).
    [CrossRef]

2004 (3)

I.  Marcikic, H.  de Riedmatten, W.  Tittel, H.  Zbinden, M.  Legré, N.  Gisin, “Distribution of Time-Bin Entangled Qubits over 50 km of Optical Fiber,” Phys. Rev. Lett. 93, 180502 (2004).
[CrossRef] [PubMed]

R.  Ursin, T.  Jennewein, M.  Aspelmeyer, R.  Kaltenbaek, M.  Lindenthal, P.  Walther, A.  Zeilinger, “Quantum teleportation across the Danube,” Nature 430, 849 (2004).
[CrossRef] [PubMed]

A.  Poppe, A.  Fedrizzi, R.  Ursin, H.R.  Böhm, T.  Lorünser, O.  Maurhardt, M.  Peev, M.  Suda, C.  Kurtsiefer, H.  Weinfurter, T.  Jennewein, A.  Zeilinger, “Practical quantum key distribution with polarization entangled photons,” Opt. Express 12, 3865–3871 (2004). http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-16-3865
[CrossRef] [PubMed]

2003 (3)

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

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

M.  Aspelmeyer, T.  Jennewein, M.  Pfenningbauer, W.R.  Leeb, A.  Zeilinger, “Long-distance quantum communication with entangled photons using satellites,” IEEE J. Sel. Top. Quantum Electron. 9, 1541–1551 (2003).
[CrossRef]

2002 (6)

J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, P.  Knight, “Ground to satellite secure key exchange using quantum cryptography,” New J. Phys. 4, 82, (2002).
[CrossRef]

J.E.  Nordholt, R.J.  Hughes, G.L.  Morgan, C.G.  Peterson, C.C.  Wipf, “Present and future quantum key distribution”, Proc. SPIE 4635, 116–126 (2002).
[CrossRef]

E.  Waks, A.  Zeevi, Y.  Yamamoto, “Security of quantum key distribution with entangled photons against individual attacks,” Phys. Rev. A 65, 052310 (2002).
[CrossRef]

R.J.  Hughes, J.E.  Nordholt, D.  Derkacs, C.G.  Peterson, “Practical free-space quantum key distribution over 10 km in daylight and at night,” New J. Phys. 4, 43 (2002).
[CrossRef]

C.  Kurtsiefer, P.  Zarda, M.  Halder, H.  Weinfurter, P.M.  Gorman, P.R.  Tapster, J.G.  Rarity, “A step towards global key distribution,” Nature 419, 450 (2002).
[CrossRef] [PubMed]

N.  Gisin, G.  Ribordy, W.  Tittel, H.  Zbinden, “Quantum Cryptography,” Rev. Mod. Phys. 74, 145–195 (2002).
[CrossRef]

2001 (1)

J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, “Secure free-space key exchange to 1.9 km and beyond,” J. Mod. Opt. 48, 1887–1901 (2001).

2000 (3)

R.J.  Hughes, W.T.  Buttler, P.G.  Kwiat, S.K.  Lamoreaux, G.L.  Morgan, J.E.  Nordholt, C.G.  Peterson, “Free-space quantum key distribution in daylight,” J. Mod. Opt. 47, 549–562, (2000).

T.  Jennewein, C.  Simon, G.  Weihs, H.  Weinfurter, A.  Zeilinger, “Quantum Cryptography with Entangled Photons,” Phys. Rev. Lett. 84, 4729–4732 (2000).
[CrossRef] [PubMed]

W. T.  Buttler, R. J.  Hughes, S. K.  Lamoreaux, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, “Daylight quantum key distribution over 1.6 km,” Phys. Rev. Lett. 84, 5652–5655 (2000).
[CrossRef] [PubMed]

1999 (1)

N.  Lütkenhaus, “Estimates for practical quantum cryptography,” Phys. Rev. A 59, 3301–3319 (1999).
[CrossRef]

1998 (3)

W. T.  Buttler, R. J.  Hughes, P. G.  Kwiat, S. K.  Lamoreaux, G. G.  Luther, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, C. M.  Simmons, “Practical free-space quantum key distribution over 1 km,” Phys. Rev. Lett., 81, 3283–3286 (1998).
[CrossRef]

G.  Weihs, T.  Jennewein, C.  Simon, H.  Weinfurter, A.  Zeilinger, “Violation of Bell’s Inequality under Strict Einstein Locality Conditions,” Phys. Rev. Lett. 81, 5039–5043 (1998).
[CrossRef]

W.  Tittel, J.  Brendel, H.  Zbinden, N.  Gisin, “Violation of Bell Inequalities by Photons More Than 10 km Apart,” Phys. Rev. Lett. 81, 3563–3566 (1998).
[CrossRef]

1995 (1)

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A.V.  Sergienko, Y.  Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).
[CrossRef] [PubMed]

1994 (1)

P.R.  Tapster, J.G.  Rarity, P.C.M.  Owens, “Violation of Bell’s Inequality over 4 km of Optical Fiber,” Phys. Rev. Lett. 73, 1923–1926 (1994).
[CrossRef] [PubMed]

1991 (1)

S.F.  Seward, P.R.  Tapster, J.G.  Walker, J.G.  Rarity, “Daylight demonstration of low-light-level communication system using correlated photon pairs,” Quantum Opt. 3, 201–207 (1991).
[CrossRef]

1986 (1)

C. K.  Hong, L.  Mandel, “Experimental realization of a localized one-photon state,” Phys. Rev. Lett. 56, 58–60 (1986).
[CrossRef] [PubMed]

1985 (1)

1984 (1)

1969 (1)

J.F.  Clauser, M.A.  Horne, A.  Shimony, R.  Holt, “Proposed experiment to test local hidden-variable theories,” Phys. Rev. Lett. 23, 880–884 (1969).
[CrossRef]

1964 (1)

J.  Bell, “On the Einstein-Podolsky-Rosen Paradox,” Physics 1, 195–200 (1964).

Alados Arboledas, L.

The transmission of 800nm light from the whole vertical atmosphere is about 80% under good weather conditions [18,19]. The horizontal attenuation coefficient measured in Vienna was approximately ?=0.05km-1. The horizontal distance with the same attenuation as the whole atmosphere vertically is, L=-ln(0.8)/?=4.5km. H.  Horwath, L.  Alados Arboledas, F.J.  Olmo, O.  Jovanovi?, M.  Gangl, W.  Kaller, C.  Sánchez, H.  Sauerzopf, S.  Seidl, “Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing,” Journal of Geophysical Research (Atmospheres) 107, No. D19, AAC 9 (2002).

Albrecht, B.A.

C.F.  Bohren, B.A.  Albrecht, Atmospheric Thermodynamics, (Oxford University Press, New York,1988).

Aspelmeyer, M.

R.  Ursin, T.  Jennewein, M.  Aspelmeyer, R.  Kaltenbaek, M.  Lindenthal, P.  Walther, A.  Zeilinger, “Quantum teleportation across the Danube,” Nature 430, 849 (2004).
[CrossRef] [PubMed]

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

M.  Aspelmeyer, T.  Jennewein, M.  Pfenningbauer, W.R.  Leeb, A.  Zeilinger, “Long-distance quantum communication with entangled photons using satellites,” IEEE J. Sel. Top. Quantum Electron. 9, 1541–1551 (2003).
[CrossRef]

Bell, J.

J.  Bell, “On the Einstein-Podolsky-Rosen Paradox,” Physics 1, 195–200 (1964).

Böhm, H. R.

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

Böhm, H.R.

Bohren, C.F.

C.F.  Bohren, B.A.  Albrecht, Atmospheric Thermodynamics, (Oxford University Press, New York,1988).

Brendel, J.

W.  Tittel, J.  Brendel, H.  Zbinden, N.  Gisin, “Violation of Bell Inequalities by Photons More Than 10 km Apart,” Phys. Rev. Lett. 81, 3563–3566 (1998).
[CrossRef]

Buttler, W. T.

W. T.  Buttler, R. J.  Hughes, S. K.  Lamoreaux, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, “Daylight quantum key distribution over 1.6 km,” Phys. Rev. Lett. 84, 5652–5655 (2000).
[CrossRef] [PubMed]

W. T.  Buttler, R. J.  Hughes, P. G.  Kwiat, S. K.  Lamoreaux, G. G.  Luther, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, C. M.  Simmons, “Practical free-space quantum key distribution over 1 km,” Phys. Rev. Lett., 81, 3283–3286 (1998).
[CrossRef]

Buttler, W.T.

R.J.  Hughes, W.T.  Buttler, P.G.  Kwiat, S.K.  Lamoreaux, G.L.  Morgan, J.E.  Nordholt, C.G.  Peterson, “Free-space quantum key distribution in daylight,” J. Mod. Opt. 47, 549–562, (2000).

Clauser, J.F.

J.F.  Clauser, M.A.  Horne, A.  Shimony, R.  Holt, “Proposed experiment to test local hidden-variable theories,” Phys. Rev. Lett. 23, 880–884 (1969).
[CrossRef]

de Riedmatten, H.

I.  Marcikic, H.  de Riedmatten, W.  Tittel, H.  Zbinden, M.  Legré, N.  Gisin, “Distribution of Time-Bin Entangled Qubits over 50 km of Optical Fiber,” Phys. Rev. Lett. 93, 180502 (2004).
[CrossRef] [PubMed]

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

Derkacs, D.

R.J.  Hughes, J.E.  Nordholt, D.  Derkacs, C.G.  Peterson, “Practical free-space quantum key distribution over 10 km in daylight and at night,” New J. Phys. 4, 43 (2002).
[CrossRef]

Fedrizzi, A.

Friberg, S.R.

Gangl, M.

The transmission of 800nm light from the whole vertical atmosphere is about 80% under good weather conditions [18,19]. The horizontal attenuation coefficient measured in Vienna was approximately ?=0.05km-1. The horizontal distance with the same attenuation as the whole atmosphere vertically is, L=-ln(0.8)/?=4.5km. H.  Horwath, L.  Alados Arboledas, F.J.  Olmo, O.  Jovanovi?, M.  Gangl, W.  Kaller, C.  Sánchez, H.  Sauerzopf, S.  Seidl, “Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing,” Journal of Geophysical Research (Atmospheres) 107, No. D19, AAC 9 (2002).

Gisin, N.

I.  Marcikic, H.  de Riedmatten, W.  Tittel, H.  Zbinden, M.  Legré, N.  Gisin, “Distribution of Time-Bin Entangled Qubits over 50 km of Optical Fiber,” Phys. Rev. Lett. 93, 180502 (2004).
[CrossRef] [PubMed]

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

N.  Gisin, G.  Ribordy, W.  Tittel, H.  Zbinden, “Quantum Cryptography,” Rev. Mod. Phys. 74, 145–195 (2002).
[CrossRef]

W.  Tittel, J.  Brendel, H.  Zbinden, N.  Gisin, “Violation of Bell Inequalities by Photons More Than 10 km Apart,” Phys. Rev. Lett. 81, 3563–3566 (1998).
[CrossRef]

Gorman, P.M.

C.  Kurtsiefer, P.  Zarda, M.  Halder, H.  Weinfurter, P.M.  Gorman, P.R.  Tapster, J.G.  Rarity, “A step towards global key distribution,” Nature 419, 450 (2002).
[CrossRef] [PubMed]

J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, P.  Knight, “Ground to satellite secure key exchange using quantum cryptography,” New J. Phys. 4, 82, (2002).
[CrossRef]

J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, “Secure free-space key exchange to 1.9 km and beyond,” J. Mod. Opt. 48, 1887–1901 (2001).

Gyatso, T.

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

Halder, M.

C.  Kurtsiefer, P.  Zarda, M.  Halder, H.  Weinfurter, P.M.  Gorman, P.R.  Tapster, J.G.  Rarity, “A step towards global key distribution,” Nature 419, 450 (2002).
[CrossRef] [PubMed]

Holt, R.

J.F.  Clauser, M.A.  Horne, A.  Shimony, R.  Holt, “Proposed experiment to test local hidden-variable theories,” Phys. Rev. Lett. 23, 880–884 (1969).
[CrossRef]

Hong, C. K.

C. K.  Hong, L.  Mandel, “Experimental realization of a localized one-photon state,” Phys. Rev. Lett. 56, 58–60 (1986).
[CrossRef] [PubMed]

Hong, C.K.

Horne, M.A.

J.F.  Clauser, M.A.  Horne, A.  Shimony, R.  Holt, “Proposed experiment to test local hidden-variable theories,” Phys. Rev. Lett. 23, 880–884 (1969).
[CrossRef]

Horwath, H.

The transmission of 800nm light from the whole vertical atmosphere is about 80% under good weather conditions [18,19]. The horizontal attenuation coefficient measured in Vienna was approximately ?=0.05km-1. The horizontal distance with the same attenuation as the whole atmosphere vertically is, L=-ln(0.8)/?=4.5km. H.  Horwath, L.  Alados Arboledas, F.J.  Olmo, O.  Jovanovi?, M.  Gangl, W.  Kaller, C.  Sánchez, H.  Sauerzopf, S.  Seidl, “Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing,” Journal of Geophysical Research (Atmospheres) 107, No. D19, AAC 9 (2002).

Hughes, R. J.

W. T.  Buttler, R. J.  Hughes, S. K.  Lamoreaux, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, “Daylight quantum key distribution over 1.6 km,” Phys. Rev. Lett. 84, 5652–5655 (2000).
[CrossRef] [PubMed]

W. T.  Buttler, R. J.  Hughes, P. G.  Kwiat, S. K.  Lamoreaux, G. G.  Luther, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, C. M.  Simmons, “Practical free-space quantum key distribution over 1 km,” Phys. Rev. Lett., 81, 3283–3286 (1998).
[CrossRef]

Hughes, R.J.

R.J.  Hughes, J.E.  Nordholt, D.  Derkacs, C.G.  Peterson, “Practical free-space quantum key distribution over 10 km in daylight and at night,” New J. Phys. 4, 43 (2002).
[CrossRef]

J.E.  Nordholt, R.J.  Hughes, G.L.  Morgan, C.G.  Peterson, C.C.  Wipf, “Present and future quantum key distribution”, Proc. SPIE 4635, 116–126 (2002).
[CrossRef]

R.J.  Hughes, W.T.  Buttler, P.G.  Kwiat, S.K.  Lamoreaux, G.L.  Morgan, J.E.  Nordholt, C.G.  Peterson, “Free-space quantum key distribution in daylight,” J. Mod. Opt. 47, 549–562, (2000).

Jennewein, T.

A.  Poppe, A.  Fedrizzi, R.  Ursin, H.R.  Böhm, T.  Lorünser, O.  Maurhardt, M.  Peev, M.  Suda, C.  Kurtsiefer, H.  Weinfurter, T.  Jennewein, A.  Zeilinger, “Practical quantum key distribution with polarization entangled photons,” Opt. Express 12, 3865–3871 (2004). http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-16-3865
[CrossRef] [PubMed]

R.  Ursin, T.  Jennewein, M.  Aspelmeyer, R.  Kaltenbaek, M.  Lindenthal, P.  Walther, A.  Zeilinger, “Quantum teleportation across the Danube,” Nature 430, 849 (2004).
[CrossRef] [PubMed]

M.  Aspelmeyer, T.  Jennewein, M.  Pfenningbauer, W.R.  Leeb, A.  Zeilinger, “Long-distance quantum communication with entangled photons using satellites,” IEEE J. Sel. Top. Quantum Electron. 9, 1541–1551 (2003).
[CrossRef]

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

T.  Jennewein, C.  Simon, G.  Weihs, H.  Weinfurter, A.  Zeilinger, “Quantum Cryptography with Entangled Photons,” Phys. Rev. Lett. 84, 4729–4732 (2000).
[CrossRef] [PubMed]

G.  Weihs, T.  Jennewein, C.  Simon, H.  Weinfurter, A.  Zeilinger, “Violation of Bell’s Inequality under Strict Einstein Locality Conditions,” Phys. Rev. Lett. 81, 5039–5043 (1998).
[CrossRef]

Jovanovic, O.

The transmission of 800nm light from the whole vertical atmosphere is about 80% under good weather conditions [18,19]. The horizontal attenuation coefficient measured in Vienna was approximately ?=0.05km-1. The horizontal distance with the same attenuation as the whole atmosphere vertically is, L=-ln(0.8)/?=4.5km. H.  Horwath, L.  Alados Arboledas, F.J.  Olmo, O.  Jovanovi?, M.  Gangl, W.  Kaller, C.  Sánchez, H.  Sauerzopf, S.  Seidl, “Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing,” Journal of Geophysical Research (Atmospheres) 107, No. D19, AAC 9 (2002).

Kaller, W.

The transmission of 800nm light from the whole vertical atmosphere is about 80% under good weather conditions [18,19]. The horizontal attenuation coefficient measured in Vienna was approximately ?=0.05km-1. The horizontal distance with the same attenuation as the whole atmosphere vertically is, L=-ln(0.8)/?=4.5km. H.  Horwath, L.  Alados Arboledas, F.J.  Olmo, O.  Jovanovi?, M.  Gangl, W.  Kaller, C.  Sánchez, H.  Sauerzopf, S.  Seidl, “Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing,” Journal of Geophysical Research (Atmospheres) 107, No. D19, AAC 9 (2002).

Kaltenbaek, R.

R.  Ursin, T.  Jennewein, M.  Aspelmeyer, R.  Kaltenbaek, M.  Lindenthal, P.  Walther, A.  Zeilinger, “Quantum teleportation across the Danube,” Nature 430, 849 (2004).
[CrossRef] [PubMed]

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

Knight, P.

J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, P.  Knight, “Ground to satellite secure key exchange using quantum cryptography,” New J. Phys. 4, 82, (2002).
[CrossRef]

Kurtsiefer, C.

Kwiat, P. G.

W. T.  Buttler, R. J.  Hughes, P. G.  Kwiat, S. K.  Lamoreaux, G. G.  Luther, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, C. M.  Simmons, “Practical free-space quantum key distribution over 1 km,” Phys. Rev. Lett., 81, 3283–3286 (1998).
[CrossRef]

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A.V.  Sergienko, Y.  Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).
[CrossRef] [PubMed]

Kwiat, P.G.

R.J.  Hughes, W.T.  Buttler, P.G.  Kwiat, S.K.  Lamoreaux, G.L.  Morgan, J.E.  Nordholt, C.G.  Peterson, “Free-space quantum key distribution in daylight,” J. Mod. Opt. 47, 549–562, (2000).

Lamoreaux, S. K.

W. T.  Buttler, R. J.  Hughes, S. K.  Lamoreaux, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, “Daylight quantum key distribution over 1.6 km,” Phys. Rev. Lett. 84, 5652–5655 (2000).
[CrossRef] [PubMed]

W. T.  Buttler, R. J.  Hughes, P. G.  Kwiat, S. K.  Lamoreaux, G. G.  Luther, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, C. M.  Simmons, “Practical free-space quantum key distribution over 1 km,” Phys. Rev. Lett., 81, 3283–3286 (1998).
[CrossRef]

Lamoreaux, S.K.

R.J.  Hughes, W.T.  Buttler, P.G.  Kwiat, S.K.  Lamoreaux, G.L.  Morgan, J.E.  Nordholt, C.G.  Peterson, “Free-space quantum key distribution in daylight,” J. Mod. Opt. 47, 549–562, (2000).

Leeb, W.R.

M.  Aspelmeyer, T.  Jennewein, M.  Pfenningbauer, W.R.  Leeb, A.  Zeilinger, “Long-distance quantum communication with entangled photons using satellites,” IEEE J. Sel. Top. Quantum Electron. 9, 1541–1551 (2003).
[CrossRef]

Legré, M.

I.  Marcikic, H.  de Riedmatten, W.  Tittel, H.  Zbinden, M.  Legré, N.  Gisin, “Distribution of Time-Bin Entangled Qubits over 50 km of Optical Fiber,” Phys. Rev. Lett. 93, 180502 (2004).
[CrossRef] [PubMed]

Lindenthal, M.

R.  Ursin, T.  Jennewein, M.  Aspelmeyer, R.  Kaltenbaek, M.  Lindenthal, P.  Walther, A.  Zeilinger, “Quantum teleportation across the Danube,” Nature 430, 849 (2004).
[CrossRef] [PubMed]

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

Lorünser, T.

Luther, G. G.

W. T.  Buttler, R. J.  Hughes, P. G.  Kwiat, S. K.  Lamoreaux, G. G.  Luther, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, C. M.  Simmons, “Practical free-space quantum key distribution over 1 km,” Phys. Rev. Lett., 81, 3283–3286 (1998).
[CrossRef]

Lütkenhaus, N.

N.  Lütkenhaus, “Estimates for practical quantum cryptography,” Phys. Rev. A 59, 3301–3319 (1999).
[CrossRef]

Mandel, L.

Marcikic, I.

I.  Marcikic, H.  de Riedmatten, W.  Tittel, H.  Zbinden, M.  Legré, N.  Gisin, “Distribution of Time-Bin Entangled Qubits over 50 km of Optical Fiber,” Phys. Rev. Lett. 93, 180502 (2004).
[CrossRef] [PubMed]

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

Mattle, K.

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A.V.  Sergienko, Y.  Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).
[CrossRef] [PubMed]

Maurhardt, O.

Molina-Terriza, G.

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

Morgan, G. L.

W. T.  Buttler, R. J.  Hughes, S. K.  Lamoreaux, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, “Daylight quantum key distribution over 1.6 km,” Phys. Rev. Lett. 84, 5652–5655 (2000).
[CrossRef] [PubMed]

W. T.  Buttler, R. J.  Hughes, P. G.  Kwiat, S. K.  Lamoreaux, G. G.  Luther, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, C. M.  Simmons, “Practical free-space quantum key distribution over 1 km,” Phys. Rev. Lett., 81, 3283–3286 (1998).
[CrossRef]

Morgan, G.L.

J.E.  Nordholt, R.J.  Hughes, G.L.  Morgan, C.G.  Peterson, C.C.  Wipf, “Present and future quantum key distribution”, Proc. SPIE 4635, 116–126 (2002).
[CrossRef]

R.J.  Hughes, W.T.  Buttler, P.G.  Kwiat, S.K.  Lamoreaux, G.L.  Morgan, J.E.  Nordholt, C.G.  Peterson, “Free-space quantum key distribution in daylight,” J. Mod. Opt. 47, 549–562, (2000).

Nordholt, J. E.

W. T.  Buttler, R. J.  Hughes, S. K.  Lamoreaux, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, “Daylight quantum key distribution over 1.6 km,” Phys. Rev. Lett. 84, 5652–5655 (2000).
[CrossRef] [PubMed]

W. T.  Buttler, R. J.  Hughes, P. G.  Kwiat, S. K.  Lamoreaux, G. G.  Luther, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, C. M.  Simmons, “Practical free-space quantum key distribution over 1 km,” Phys. Rev. Lett., 81, 3283–3286 (1998).
[CrossRef]

Nordholt, J.E.

R.J.  Hughes, J.E.  Nordholt, D.  Derkacs, C.G.  Peterson, “Practical free-space quantum key distribution over 10 km in daylight and at night,” New J. Phys. 4, 43 (2002).
[CrossRef]

J.E.  Nordholt, R.J.  Hughes, G.L.  Morgan, C.G.  Peterson, C.C.  Wipf, “Present and future quantum key distribution”, Proc. SPIE 4635, 116–126 (2002).
[CrossRef]

R.J.  Hughes, W.T.  Buttler, P.G.  Kwiat, S.K.  Lamoreaux, G.L.  Morgan, J.E.  Nordholt, C.G.  Peterson, “Free-space quantum key distribution in daylight,” J. Mod. Opt. 47, 549–562, (2000).

Olmo, F.J.

The transmission of 800nm light from the whole vertical atmosphere is about 80% under good weather conditions [18,19]. The horizontal attenuation coefficient measured in Vienna was approximately ?=0.05km-1. The horizontal distance with the same attenuation as the whole atmosphere vertically is, L=-ln(0.8)/?=4.5km. H.  Horwath, L.  Alados Arboledas, F.J.  Olmo, O.  Jovanovi?, M.  Gangl, W.  Kaller, C.  Sánchez, H.  Sauerzopf, S.  Seidl, “Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing,” Journal of Geophysical Research (Atmospheres) 107, No. D19, AAC 9 (2002).

Owens, P.C.M.

P.R.  Tapster, J.G.  Rarity, P.C.M.  Owens, “Violation of Bell’s Inequality over 4 km of Optical Fiber,” Phys. Rev. Lett. 73, 1923–1926 (1994).
[CrossRef] [PubMed]

Peev, M.

Peterson, C. G.

W. T.  Buttler, R. J.  Hughes, S. K.  Lamoreaux, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, “Daylight quantum key distribution over 1.6 km,” Phys. Rev. Lett. 84, 5652–5655 (2000).
[CrossRef] [PubMed]

W. T.  Buttler, R. J.  Hughes, P. G.  Kwiat, S. K.  Lamoreaux, G. G.  Luther, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, C. M.  Simmons, “Practical free-space quantum key distribution over 1 km,” Phys. Rev. Lett., 81, 3283–3286 (1998).
[CrossRef]

Peterson, C.G.

R.J.  Hughes, J.E.  Nordholt, D.  Derkacs, C.G.  Peterson, “Practical free-space quantum key distribution over 10 km in daylight and at night,” New J. Phys. 4, 43 (2002).
[CrossRef]

J.E.  Nordholt, R.J.  Hughes, G.L.  Morgan, C.G.  Peterson, C.C.  Wipf, “Present and future quantum key distribution”, Proc. SPIE 4635, 116–126 (2002).
[CrossRef]

R.J.  Hughes, W.T.  Buttler, P.G.  Kwiat, S.K.  Lamoreaux, G.L.  Morgan, J.E.  Nordholt, C.G.  Peterson, “Free-space quantum key distribution in daylight,” J. Mod. Opt. 47, 549–562, (2000).

Pfenningbauer, M.

M.  Aspelmeyer, T.  Jennewein, M.  Pfenningbauer, W.R.  Leeb, A.  Zeilinger, “Long-distance quantum communication with entangled photons using satellites,” IEEE J. Sel. Top. Quantum Electron. 9, 1541–1551 (2003).
[CrossRef]

Poppe, A.

A.  Poppe, A.  Fedrizzi, R.  Ursin, H.R.  Böhm, T.  Lorünser, O.  Maurhardt, M.  Peev, M.  Suda, C.  Kurtsiefer, H.  Weinfurter, T.  Jennewein, A.  Zeilinger, “Practical quantum key distribution with polarization entangled photons,” Opt. Express 12, 3865–3871 (2004). http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-16-3865
[CrossRef] [PubMed]

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

Rarity, J.G.

J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, P.  Knight, “Ground to satellite secure key exchange using quantum cryptography,” New J. Phys. 4, 82, (2002).
[CrossRef]

C.  Kurtsiefer, P.  Zarda, M.  Halder, H.  Weinfurter, P.M.  Gorman, P.R.  Tapster, J.G.  Rarity, “A step towards global key distribution,” Nature 419, 450 (2002).
[CrossRef] [PubMed]

J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, “Secure free-space key exchange to 1.9 km and beyond,” J. Mod. Opt. 48, 1887–1901 (2001).

P.R.  Tapster, J.G.  Rarity, P.C.M.  Owens, “Violation of Bell’s Inequality over 4 km of Optical Fiber,” Phys. Rev. Lett. 73, 1923–1926 (1994).
[CrossRef] [PubMed]

S.F.  Seward, P.R.  Tapster, J.G.  Walker, J.G.  Rarity, “Daylight demonstration of low-light-level communication system using correlated photon pairs,” Quantum Opt. 3, 201–207 (1991).
[CrossRef]

Resch, K.

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

Ribordy, G.

N.  Gisin, G.  Ribordy, W.  Tittel, H.  Zbinden, “Quantum Cryptography,” Rev. Mod. Phys. 74, 145–195 (2002).
[CrossRef]

Sánchez, C.

The transmission of 800nm light from the whole vertical atmosphere is about 80% under good weather conditions [18,19]. The horizontal attenuation coefficient measured in Vienna was approximately ?=0.05km-1. The horizontal distance with the same attenuation as the whole atmosphere vertically is, L=-ln(0.8)/?=4.5km. H.  Horwath, L.  Alados Arboledas, F.J.  Olmo, O.  Jovanovi?, M.  Gangl, W.  Kaller, C.  Sánchez, H.  Sauerzopf, S.  Seidl, “Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing,” Journal of Geophysical Research (Atmospheres) 107, No. D19, AAC 9 (2002).

Sauerzopf, H.

The transmission of 800nm light from the whole vertical atmosphere is about 80% under good weather conditions [18,19]. The horizontal attenuation coefficient measured in Vienna was approximately ?=0.05km-1. The horizontal distance with the same attenuation as the whole atmosphere vertically is, L=-ln(0.8)/?=4.5km. H.  Horwath, L.  Alados Arboledas, F.J.  Olmo, O.  Jovanovi?, M.  Gangl, W.  Kaller, C.  Sánchez, H.  Sauerzopf, S.  Seidl, “Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing,” Journal of Geophysical Research (Atmospheres) 107, No. D19, AAC 9 (2002).

Seidl, S.

The transmission of 800nm light from the whole vertical atmosphere is about 80% under good weather conditions [18,19]. The horizontal attenuation coefficient measured in Vienna was approximately ?=0.05km-1. The horizontal distance with the same attenuation as the whole atmosphere vertically is, L=-ln(0.8)/?=4.5km. H.  Horwath, L.  Alados Arboledas, F.J.  Olmo, O.  Jovanovi?, M.  Gangl, W.  Kaller, C.  Sánchez, H.  Sauerzopf, S.  Seidl, “Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing,” Journal of Geophysical Research (Atmospheres) 107, No. D19, AAC 9 (2002).

Sergienko, A.V.

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A.V.  Sergienko, Y.  Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).
[CrossRef] [PubMed]

Seward, S.F.

S.F.  Seward, P.R.  Tapster, J.G.  Walker, J.G.  Rarity, “Daylight demonstration of low-light-level communication system using correlated photon pairs,” Quantum Opt. 3, 201–207 (1991).
[CrossRef]

Shih, Y.

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A.V.  Sergienko, Y.  Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).
[CrossRef] [PubMed]

Shimony, A.

J.F.  Clauser, M.A.  Horne, A.  Shimony, R.  Holt, “Proposed experiment to test local hidden-variable theories,” Phys. Rev. Lett. 23, 880–884 (1969).
[CrossRef]

Simmons, C. M.

W. T.  Buttler, R. J.  Hughes, P. G.  Kwiat, S. K.  Lamoreaux, G. G.  Luther, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, C. M.  Simmons, “Practical free-space quantum key distribution over 1 km,” Phys. Rev. Lett., 81, 3283–3286 (1998).
[CrossRef]

Simon, C.

T.  Jennewein, C.  Simon, G.  Weihs, H.  Weinfurter, A.  Zeilinger, “Quantum Cryptography with Entangled Photons,” Phys. Rev. Lett. 84, 4729–4732 (2000).
[CrossRef] [PubMed]

G.  Weihs, T.  Jennewein, C.  Simon, H.  Weinfurter, A.  Zeilinger, “Violation of Bell’s Inequality under Strict Einstein Locality Conditions,” Phys. Rev. Lett. 81, 5039–5043 (1998).
[CrossRef]

Suda, M.

Tapster, P.R.

J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, P.  Knight, “Ground to satellite secure key exchange using quantum cryptography,” New J. Phys. 4, 82, (2002).
[CrossRef]

C.  Kurtsiefer, P.  Zarda, M.  Halder, H.  Weinfurter, P.M.  Gorman, P.R.  Tapster, J.G.  Rarity, “A step towards global key distribution,” Nature 419, 450 (2002).
[CrossRef] [PubMed]

J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, “Secure free-space key exchange to 1.9 km and beyond,” J. Mod. Opt. 48, 1887–1901 (2001).

P.R.  Tapster, J.G.  Rarity, P.C.M.  Owens, “Violation of Bell’s Inequality over 4 km of Optical Fiber,” Phys. Rev. Lett. 73, 1923–1926 (1994).
[CrossRef] [PubMed]

S.F.  Seward, P.R.  Tapster, J.G.  Walker, J.G.  Rarity, “Daylight demonstration of low-light-level communication system using correlated photon pairs,” Quantum Opt. 3, 201–207 (1991).
[CrossRef]

Taraba, M.

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

Tittel, W.

I.  Marcikic, H.  de Riedmatten, W.  Tittel, H.  Zbinden, M.  Legré, N.  Gisin, “Distribution of Time-Bin Entangled Qubits over 50 km of Optical Fiber,” Phys. Rev. Lett. 93, 180502 (2004).
[CrossRef] [PubMed]

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

N.  Gisin, G.  Ribordy, W.  Tittel, H.  Zbinden, “Quantum Cryptography,” Rev. Mod. Phys. 74, 145–195 (2002).
[CrossRef]

W.  Tittel, J.  Brendel, H.  Zbinden, N.  Gisin, “Violation of Bell Inequalities by Photons More Than 10 km Apart,” Phys. Rev. Lett. 81, 3563–3566 (1998).
[CrossRef]

Ursin, R.

R.  Ursin, T.  Jennewein, M.  Aspelmeyer, R.  Kaltenbaek, M.  Lindenthal, P.  Walther, A.  Zeilinger, “Quantum teleportation across the Danube,” Nature 430, 849 (2004).
[CrossRef] [PubMed]

A.  Poppe, A.  Fedrizzi, R.  Ursin, H.R.  Böhm, T.  Lorünser, O.  Maurhardt, M.  Peev, M.  Suda, C.  Kurtsiefer, H.  Weinfurter, T.  Jennewein, A.  Zeilinger, “Practical quantum key distribution with polarization entangled photons,” Opt. Express 12, 3865–3871 (2004). http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-16-3865
[CrossRef] [PubMed]

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

Waks, E.

E.  Waks, A.  Zeevi, Y.  Yamamoto, “Security of quantum key distribution with entangled photons against individual attacks,” Phys. Rev. A 65, 052310 (2002).
[CrossRef]

Walker, J.G.

S.F.  Seward, P.R.  Tapster, J.G.  Walker, J.G.  Rarity, “Daylight demonstration of low-light-level communication system using correlated photon pairs,” Quantum Opt. 3, 201–207 (1991).
[CrossRef]

Walther, P.

R.  Ursin, T.  Jennewein, M.  Aspelmeyer, R.  Kaltenbaek, M.  Lindenthal, P.  Walther, A.  Zeilinger, “Quantum teleportation across the Danube,” Nature 430, 849 (2004).
[CrossRef] [PubMed]

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

Weihs, G.

T.  Jennewein, C.  Simon, G.  Weihs, H.  Weinfurter, A.  Zeilinger, “Quantum Cryptography with Entangled Photons,” Phys. Rev. Lett. 84, 4729–4732 (2000).
[CrossRef] [PubMed]

G.  Weihs, T.  Jennewein, C.  Simon, H.  Weinfurter, A.  Zeilinger, “Violation of Bell’s Inequality under Strict Einstein Locality Conditions,” Phys. Rev. Lett. 81, 5039–5043 (1998).
[CrossRef]

Weinfurter, H.

A.  Poppe, A.  Fedrizzi, R.  Ursin, H.R.  Böhm, T.  Lorünser, O.  Maurhardt, M.  Peev, M.  Suda, C.  Kurtsiefer, H.  Weinfurter, T.  Jennewein, A.  Zeilinger, “Practical quantum key distribution with polarization entangled photons,” Opt. Express 12, 3865–3871 (2004). http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-16-3865
[CrossRef] [PubMed]

C.  Kurtsiefer, P.  Zarda, M.  Halder, H.  Weinfurter, P.M.  Gorman, P.R.  Tapster, J.G.  Rarity, “A step towards global key distribution,” Nature 419, 450 (2002).
[CrossRef] [PubMed]

T.  Jennewein, C.  Simon, G.  Weihs, H.  Weinfurter, A.  Zeilinger, “Quantum Cryptography with Entangled Photons,” Phys. Rev. Lett. 84, 4729–4732 (2000).
[CrossRef] [PubMed]

G.  Weihs, T.  Jennewein, C.  Simon, H.  Weinfurter, A.  Zeilinger, “Violation of Bell’s Inequality under Strict Einstein Locality Conditions,” Phys. Rev. Lett. 81, 5039–5043 (1998).
[CrossRef]

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A.V.  Sergienko, Y.  Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).
[CrossRef] [PubMed]

Wipf, C.C.

J.E.  Nordholt, R.J.  Hughes, G.L.  Morgan, C.G.  Peterson, C.C.  Wipf, “Present and future quantum key distribution”, Proc. SPIE 4635, 116–126 (2002).
[CrossRef]

Yamamoto, Y.

E.  Waks, A.  Zeevi, Y.  Yamamoto, “Security of quantum key distribution with entangled photons against individual attacks,” Phys. Rev. A 65, 052310 (2002).
[CrossRef]

Zarda, P.

C.  Kurtsiefer, P.  Zarda, M.  Halder, H.  Weinfurter, P.M.  Gorman, P.R.  Tapster, J.G.  Rarity, “A step towards global key distribution,” Nature 419, 450 (2002).
[CrossRef] [PubMed]

Zbinden, H.

I.  Marcikic, H.  de Riedmatten, W.  Tittel, H.  Zbinden, M.  Legré, N.  Gisin, “Distribution of Time-Bin Entangled Qubits over 50 km of Optical Fiber,” Phys. Rev. Lett. 93, 180502 (2004).
[CrossRef] [PubMed]

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

N.  Gisin, G.  Ribordy, W.  Tittel, H.  Zbinden, “Quantum Cryptography,” Rev. Mod. Phys. 74, 145–195 (2002).
[CrossRef]

W.  Tittel, J.  Brendel, H.  Zbinden, N.  Gisin, “Violation of Bell Inequalities by Photons More Than 10 km Apart,” Phys. Rev. Lett. 81, 3563–3566 (1998).
[CrossRef]

Zeevi, A.

E.  Waks, A.  Zeevi, Y.  Yamamoto, “Security of quantum key distribution with entangled photons against individual attacks,” Phys. Rev. A 65, 052310 (2002).
[CrossRef]

Zeilinger, A.

R.  Ursin, T.  Jennewein, M.  Aspelmeyer, R.  Kaltenbaek, M.  Lindenthal, P.  Walther, A.  Zeilinger, “Quantum teleportation across the Danube,” Nature 430, 849 (2004).
[CrossRef] [PubMed]

A.  Poppe, A.  Fedrizzi, R.  Ursin, H.R.  Böhm, T.  Lorünser, O.  Maurhardt, M.  Peev, M.  Suda, C.  Kurtsiefer, H.  Weinfurter, T.  Jennewein, A.  Zeilinger, “Practical quantum key distribution with polarization entangled photons,” Opt. Express 12, 3865–3871 (2004). http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-16-3865
[CrossRef] [PubMed]

M.  Aspelmeyer, T.  Jennewein, M.  Pfenningbauer, W.R.  Leeb, A.  Zeilinger, “Long-distance quantum communication with entangled photons using satellites,” IEEE J. Sel. Top. Quantum Electron. 9, 1541–1551 (2003).
[CrossRef]

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

T.  Jennewein, C.  Simon, G.  Weihs, H.  Weinfurter, A.  Zeilinger, “Quantum Cryptography with Entangled Photons,” Phys. Rev. Lett. 84, 4729–4732 (2000).
[CrossRef] [PubMed]

G.  Weihs, T.  Jennewein, C.  Simon, H.  Weinfurter, A.  Zeilinger, “Violation of Bell’s Inequality under Strict Einstein Locality Conditions,” Phys. Rev. Lett. 81, 5039–5043 (1998).
[CrossRef]

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A.V.  Sergienko, Y.  Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).
[CrossRef] [PubMed]

Appl. Opt. (1)

IEEE J. Sel. Top. Quantum Electron. (1)

M.  Aspelmeyer, T.  Jennewein, M.  Pfenningbauer, W.R.  Leeb, A.  Zeilinger, “Long-distance quantum communication with entangled photons using satellites,” IEEE J. Sel. Top. Quantum Electron. 9, 1541–1551 (2003).
[CrossRef]

J. Mod. Opt. (2)

R.J.  Hughes, W.T.  Buttler, P.G.  Kwiat, S.K.  Lamoreaux, G.L.  Morgan, J.E.  Nordholt, C.G.  Peterson, “Free-space quantum key distribution in daylight,” J. Mod. Opt. 47, 549–562, (2000).

J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, “Secure free-space key exchange to 1.9 km and beyond,” J. Mod. Opt. 48, 1887–1901 (2001).

J. Opt. Soc. Am. B (1)

Nature (3)

C.  Kurtsiefer, P.  Zarda, M.  Halder, H.  Weinfurter, P.M.  Gorman, P.R.  Tapster, J.G.  Rarity, “A step towards global key distribution,” Nature 419, 450 (2002).
[CrossRef] [PubMed]

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

R.  Ursin, T.  Jennewein, M.  Aspelmeyer, R.  Kaltenbaek, M.  Lindenthal, P.  Walther, A.  Zeilinger, “Quantum teleportation across the Danube,” Nature 430, 849 (2004).
[CrossRef] [PubMed]

New J. Phys. (2)

R.J.  Hughes, J.E.  Nordholt, D.  Derkacs, C.G.  Peterson, “Practical free-space quantum key distribution over 10 km in daylight and at night,” New J. Phys. 4, 43 (2002).
[CrossRef]

J.G.  Rarity, P.R.  Tapster, P.M.  Gorman, P.  Knight, “Ground to satellite secure key exchange using quantum cryptography,” New J. Phys. 4, 82, (2002).
[CrossRef]

Opt. Express (1)

Phys. Rev. A (2)

E.  Waks, A.  Zeevi, Y.  Yamamoto, “Security of quantum key distribution with entangled photons against individual attacks,” Phys. Rev. A 65, 052310 (2002).
[CrossRef]

N.  Lütkenhaus, “Estimates for practical quantum cryptography,” Phys. Rev. A 59, 3301–3319 (1999).
[CrossRef]

Phys. Rev. Lett. (10)

C. K.  Hong, L.  Mandel, “Experimental realization of a localized one-photon state,” Phys. Rev. Lett. 56, 58–60 (1986).
[CrossRef] [PubMed]

J.F.  Clauser, M.A.  Horne, A.  Shimony, R.  Holt, “Proposed experiment to test local hidden-variable theories,” Phys. Rev. Lett. 23, 880–884 (1969).
[CrossRef]

P. G.  Kwiat, K.  Mattle, H.  Weinfurter, A.  Zeilinger, A.V.  Sergienko, Y.  Shih, “New high-intensity source of polarization-entangled photon pairs,” Phys. Rev. Lett. 75, 4337–4341 (1995).
[CrossRef] [PubMed]

W. T.  Buttler, R. J.  Hughes, P. G.  Kwiat, S. K.  Lamoreaux, G. G.  Luther, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, C. M.  Simmons, “Practical free-space quantum key distribution over 1 km,” Phys. Rev. Lett., 81, 3283–3286 (1998).
[CrossRef]

W. T.  Buttler, R. J.  Hughes, S. K.  Lamoreaux, G. L.  Morgan, J. E.  Nordholt, C. G.  Peterson, “Daylight quantum key distribution over 1.6 km,” Phys. Rev. Lett. 84, 5652–5655 (2000).
[CrossRef] [PubMed]

G.  Weihs, T.  Jennewein, C.  Simon, H.  Weinfurter, A.  Zeilinger, “Violation of Bell’s Inequality under Strict Einstein Locality Conditions,” Phys. Rev. Lett. 81, 5039–5043 (1998).
[CrossRef]

T.  Jennewein, C.  Simon, G.  Weihs, H.  Weinfurter, A.  Zeilinger, “Quantum Cryptography with Entangled Photons,” Phys. Rev. Lett. 84, 4729–4732 (2000).
[CrossRef] [PubMed]

P.R.  Tapster, J.G.  Rarity, P.C.M.  Owens, “Violation of Bell’s Inequality over 4 km of Optical Fiber,” Phys. Rev. Lett. 73, 1923–1926 (1994).
[CrossRef] [PubMed]

W.  Tittel, J.  Brendel, H.  Zbinden, N.  Gisin, “Violation of Bell Inequalities by Photons More Than 10 km Apart,” Phys. Rev. Lett. 81, 3563–3566 (1998).
[CrossRef]

I.  Marcikic, H.  de Riedmatten, W.  Tittel, H.  Zbinden, M.  Legré, N.  Gisin, “Distribution of Time-Bin Entangled Qubits over 50 km of Optical Fiber,” Phys. Rev. Lett. 93, 180502 (2004).
[CrossRef] [PubMed]

Physics (1)

J.  Bell, “On the Einstein-Podolsky-Rosen Paradox,” Physics 1, 195–200 (1964).

Proc. SPIE (1)

J.E.  Nordholt, R.J.  Hughes, G.L.  Morgan, C.G.  Peterson, C.C.  Wipf, “Present and future quantum key distribution”, Proc. SPIE 4635, 116–126 (2002).
[CrossRef]

Quantum Opt. (1)

S.F.  Seward, P.R.  Tapster, J.G.  Walker, J.G.  Rarity, “Daylight demonstration of low-light-level communication system using correlated photon pairs,” Quantum Opt. 3, 201–207 (1991).
[CrossRef]

Rev. Mod. Phys. (1)

N.  Gisin, G.  Ribordy, W.  Tittel, H.  Zbinden, “Quantum Cryptography,” Rev. Mod. Phys. 74, 145–195 (2002).
[CrossRef]

Science (1)

M.  Aspelmeyer, H. R.  Böhm, T.  Gyatso, T.  Jennewein, R.  Kaltenbaek, M.  Lindenthal, G.  Molina-Terriza, A.  Poppe, K.  Resch, M.  Taraba, R.  Ursin, P.  Walther, A.  Zeilinger, “Long-Distance Free-Space Distribution of Quantum Entanglement,” Science 301, 621–623 (2003).
[CrossRef] [PubMed]

Other (3)

D.  Bouwmeester, A.  Ekert, A.  Zeilinger, Eds. The Physics of Quantum Information (Springer-Verlag, Berlin, 2000).

C.F.  Bohren, B.A.  Albrecht, Atmospheric Thermodynamics, (Oxford University Press, New York,1988).

The transmission of 800nm light from the whole vertical atmosphere is about 80% under good weather conditions [18,19]. The horizontal attenuation coefficient measured in Vienna was approximately ?=0.05km-1. The horizontal distance with the same attenuation as the whole atmosphere vertically is, L=-ln(0.8)/?=4.5km. H.  Horwath, L.  Alados Arboledas, F.J.  Olmo, O.  Jovanovi?, M.  Gangl, W.  Kaller, C.  Sánchez, H.  Sauerzopf, S.  Seidl, “Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing,” Journal of Geophysical Research (Atmospheres) 107, No. D19, AAC 9 (2002).

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Figures (1)

Fig. 1.
Fig. 1.

The layout for free-space entanglement distribution in Vienna. Alice has the single-mode fibre coupled polarization-entangled photon source (DC) and sending telescope and is located in the 19th century observatory, Kuffner Sternwarte. Bob has a receiver telescope and is located on the 46th floor of the Millennium Tower skyscraper 7.8km away. Alice measures the photons in mode A from each entangled pair using a four-channel detector, made with a 50/50 beam-splitter (BS), a half-wave plate (HWP), and polarizing beam-splitters (PBS), which measures the photon polarization in either the H/V or +/- basis. She sends the other photon in mode B, after polarization compensation (Pol.), via her telescope and free-space link, to Bob. Bob’s receiver telescope is equipped with a similar four-channel detector and can measure the polarizations in the same bases as Alice or, by rotating an extra HWP, measure another pair of complementary linear polarization bases. Alice and Bob are both equipped with time-tagging cards which record the times at which each detection event occurs. Rubidium atomic clocks provide good relative time stability. Both stations also embed a 1pps signal from the global positioning system (GPS) into their time-tag data stream to give a well-defined zero time offset. During accumulation, Bob transmits his time tags in blocks over a public internet channel to Alice. She finds the coincident photon pairs in real time by maximizing the cross-correlation of these time tags. Which of the four detector channels fired is also part of each time tag and allows Alice and Bob to determine the polarization correlations between their coincident pairs. Alice uses her polarization compensators to establish singlet-like anti-correlations between her measurements and Bob’s.

Tables (2)

Tables Icon

Table 1. Experimentally-measured coincidence rates.

Tables Icon

Table 2. The polarization correlations between the different bases.

Equations (3)

Equations on this page are rendered with MathJax. Learn more.

ψ = 1 2 ( H A V B V A H B ) ,
S = E ( φ A , φ B ) E ( φ A , φ ˜ B ) + E ( φ ˜ A , φ B ) + E ( φ ˜ A , φ ˜ B ) ,
QBER = 1 2 ( 1 S EXP S QM ) ,

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