Abstract

We present a fiber-based continuous-variable quantum key distribution system. In the scheme, a quantum signal of two non-orthogonal weak optical coherent states is sent through a fiber-based quantum channel. The receiver simultaneously measures conjugate quadratures of the light using two homodyne detectors. From the measured Q-function of the transmitted signal, we estimate the attenuation and the excess noise caused by the channel. The estimated excess noise originating from the channel and the channel attenuation including the quantum efficiency of the detection setup is investigated with respect to the detection of effective entanglement. The local oscillator is considered in the verification. We witness effective entanglement with a channel length of up to 2km.

© 2010 Optical Society of America

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2009 (2)

D. Elser, T. Bartley, B. Heim, C. Wittmann, D. Sych, and G. Leuchs, "Feasibility of free space quantum key distribution with coherent polarization states," New J. Phys. 11, 045014 (2009).
[CrossRef]

Y. Zhao, M. Heid, J. Rigas, and N. Lütkenhaus, "Asymptotic security of binary modulated continuous-variable quantum key distribution under collective attacks," Phys. Rev. A 79, 012307-14 (2009).
[CrossRef]

2008 (2)

H. Häseler, T. Moroder, and N. Lütkenhaus, "Testing quantum devices: Practical entanglement verification in bipartite optical systems," Phys. Rev. A 77, 032303-11 (2008).
[CrossRef]

S. Pirandola, S. Mancini, S. Lloyd, and S. L. Braunstein, "Continuous-variable quantum cryptography using two-way quantum communication," Nat. Phys. 4, 726-730 (2008).
[CrossRef]

2007 (7)

D. Elser, C. Wittmann, U. L. Andersen, O. Glöckl, S. Lorenz, C. Marquardt, and G. Leuchs, "Guided acoustic wave brillouin scattering in photonic crystal fibers," J. Phys. Conf. Ser. 92, 012108 (2007).
[CrossRef]

J. Lodewyck and P. Grangier, "Tight bound on the coherent-state quantum key distribution with heterodyne detection," Phys. Rev. A 76, 022332 (2007).
[CrossRef]

D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, "Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 10503 (2007).
[CrossRef]

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
[CrossRef]

T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
[CrossRef] [PubMed]

J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
[CrossRef]

B. Qi, L. Huang, L. Qian, and H. Lo, "Experimental study on the gaussian-modulated coherent-state quantum key distribution over standard telecommunication fibers," Phys. Rev. A 76, 052323-9 (2007).
[CrossRef]

2006 (4)

N. Gisin, S. Fasel, B. Kraus, H. Zbinden, and G. Ribordy, "Trojan-horse attacks on quantum-key-distribution systems," Phys. Rev. A 73, 022320 (2006).
[CrossRef]

J. Rigas, O. Gühne, and N. Lütkenhaus, "Entanglement verification for quantum-key-distribution systems with an underlying bipartite qubit-mode structure," Phys. Rev. A 73, 012341-6 (2006).
[CrossRef]

M. Legré, H. Zbinden, and N. Gisin, "Implementation of continuous variable quantum cryptography in optical fibres using a go-&-return configuration," Quantum Inf. Comput. 6, 326-335 (2006).

C. Weedbrook, A. M. Lance, W. P. Bowen, T. Symul, T. C. Ralph, and P. K. Lam, "Coherent-state quantum key distribution without random basis switching," Phys. Rev. A 73, 022316-9 (2006).
[CrossRef]

2005 (1)

A. M. Lance, T. Symul, V. Sharma, C. Weedbrook, T. C. Ralph, and P. K. Lam, "No-switching quantum key distribution using broadband modulated coherent light," Phys. Rev. Lett. 95, 180503 (2005).
[CrossRef] [PubMed]

2004 (2)

S. Lorenz, N. Korolkova, and G. Leuchs, "Continuous-variable quantum key distribution using polarization encoding and post selection," Appl. Phys. B 79, 273-277 (2004).
[CrossRef]

M. Curty, M. Lewenstein, and N. Lütkenhaus, "Entanglement as a precondition for secure quantum key distribution," Phys. Rev. Lett. 92, 217903 (2004).
[CrossRef] [PubMed]

2003 (2)

C. Dorrer, D. Kilper, H. Stuart, G. Raybon, and M. Raymer, "Linear optical sampling," IEEE Photonics Technol. Lett. 15, 1746-1748 (2003).
[CrossRef]

F. Grosshans, G. V. Assche, J. Wenger, R. Brouri, N. J. Cerf, and P. Grangier, "Quantum key distribution using gaussian-modulated coherent states," Nature 421, 238-241 (2003).
[CrossRef] [PubMed]

2002 (3)

C. Silberhorn, T. C. Ralph, N. Lütkenhaus, and G. Leuchs, "Continuous variable quantum cryptography: Beating the 3 dB loss limit," Phys. Rev. Lett. 89, 167901 (2002).
[CrossRef] [PubMed]

D. Stucki, N. Gisin, O. Guinnard, G. Ribordy, and H. Zbinden, "Quantum key distribution over 67 km with a plug&play system," New J. Phys. 4, 41 (2002).
[CrossRef]

N. Korolkova, G. Leuchs, R. Loudon, T. C. Ralph, and C. Silberhorn, "Polarization squeezing and continuous variable polarization entanglement," Phys. Rev. A 65, 052306 (2002).
[CrossRef]

2001 (1)

1999 (1)

T. C. Ralph, "Continuous variable quantum cryptography," Phys. Rev. A 61, 010303 (1999).
[CrossRef]

1995 (1)

U. Leonhardt, J. A. Vaccaro, B. Böhmer, and H. Paul, "Canonical and measured phase distributions," Phys. Rev. A 51, 84 (1995).
[CrossRef] [PubMed]

1993 (2)

U. Leonhardt and H. Paul, "Realistic optical homodyne measurements and quasi-probability distributions," Phys. Rev. A 48, 4598-4604 (1993).
[CrossRef] [PubMed]

A. Muller, J. Breguet, and N. Gisin, "Experimental demonstration of quantum cryptography using polarized photons in optical-fiber over more than 1 km," Europhys. Lett. 23, 383-388 (1993).
[CrossRef]

1992 (5)

C. Bennett, F. Bessette, G. Brassard, L. Salvail, and J. Smolin, "Experimental quantum cryptography," J. Cryptology 5, 3-28 (1992).
[CrossRef]

A. Ekert, J. Rarity, P. Tapster, and G. Palma, "Practical quantum cryptography based on 2-photon interferometry," Phys. Rev. Lett. 69, 1293-1295 (1992).
[CrossRef] [PubMed]

S. Stenholm, "Simultaneous measurement of conjugate variables," Ann. Phys. 218, 233-254 (1992).
[CrossRef]

C. H. Bennett, "Quantum cryptography using any two nonorthogonal states," Phys. Rev. Lett. 68, 3121 (1992).
[CrossRef] [PubMed]

C. H. Bennett, G. Brassard, and N. D. Mermin, "Quantum cryptography without bell’s theorem," Phys. Rev. Lett. 68, 557 (1992).
[CrossRef] [PubMed]

1984 (1)

J. Shapiro and S. Wagner, "Phase and amplitude uncertainties in heterodyne detection," IEEE J. Quantum Electron. 20, 803-813 (1984).
[CrossRef]

1965 (1)

J. A. Nelder and R. Mead, "A simplex method for function minimization," The Computer Journal 7, 308-313 (1965).

1949 (1)

C. Shannon, "Communication theory of secrecy systems," Bell Sys. Tech. J. 28, 656-715 (1949).

1926 (1)

G. Vernam, "Cipher printing telegraph systems for secret wire and radio telegraphic communications," J. Amer. Inst. Elect. Eng., 109 (1926).

Aichele, T.

Andersen, U. L.

D. Elser, C. Wittmann, U. L. Andersen, O. Glöckl, S. Lorenz, C. Marquardt, and G. Leuchs, "Guided acoustic wave brillouin scattering in photonic crystal fibers," J. Phys. Conf. Ser. 92, 012108 (2007).
[CrossRef]

Assche, G. V.

F. Grosshans, G. V. Assche, J. Wenger, R. Brouri, N. J. Cerf, and P. Grangier, "Quantum key distribution using gaussian-modulated coherent states," Nature 421, 238-241 (2003).
[CrossRef] [PubMed]

Barbieri, C.

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
[CrossRef]

Bartley, T.

D. Elser, T. Bartley, B. Heim, C. Wittmann, D. Sych, and G. Leuchs, "Feasibility of free space quantum key distribution with coherent polarization states," New J. Phys. 11, 045014 (2009).
[CrossRef]

Bennett, C.

C. Bennett, F. Bessette, G. Brassard, L. Salvail, and J. Smolin, "Experimental quantum cryptography," J. Cryptology 5, 3-28 (1992).
[CrossRef]

Bennett, C. H.

C. H. Bennett, G. Brassard, and N. D. Mermin, "Quantum cryptography without bell’s theorem," Phys. Rev. Lett. 68, 557 (1992).
[CrossRef] [PubMed]

C. H. Bennett, "Quantum cryptography using any two nonorthogonal states," Phys. Rev. Lett. 68, 3121 (1992).
[CrossRef] [PubMed]

Bessette, F.

C. Bennett, F. Bessette, G. Brassard, L. Salvail, and J. Smolin, "Experimental quantum cryptography," J. Cryptology 5, 3-28 (1992).
[CrossRef]

Blauensteiner, B.

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
[CrossRef]

Bloch, M.

J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
[CrossRef]

Böhmer, B.

U. Leonhardt, J. A. Vaccaro, B. Böhmer, and H. Paul, "Canonical and measured phase distributions," Phys. Rev. A 51, 84 (1995).
[CrossRef] [PubMed]

Bowen, W. P.

C. Weedbrook, A. M. Lance, W. P. Bowen, T. Symul, T. C. Ralph, and P. K. Lam, "Coherent-state quantum key distribution without random basis switching," Phys. Rev. A 73, 022316-9 (2006).
[CrossRef]

Brassard, G.

C. Bennett, F. Bessette, G. Brassard, L. Salvail, and J. Smolin, "Experimental quantum cryptography," J. Cryptology 5, 3-28 (1992).
[CrossRef]

C. H. Bennett, G. Brassard, and N. D. Mermin, "Quantum cryptography without bell’s theorem," Phys. Rev. Lett. 68, 557 (1992).
[CrossRef] [PubMed]

Braunstein, S. L.

S. Pirandola, S. Mancini, S. Lloyd, and S. L. Braunstein, "Continuous-variable quantum cryptography using two-way quantum communication," Nat. Phys. 4, 726-730 (2008).
[CrossRef]

Breguet, J.

A. Muller, J. Breguet, and N. Gisin, "Experimental demonstration of quantum cryptography using polarized photons in optical-fiber over more than 1 km," Europhys. Lett. 23, 383-388 (1993).
[CrossRef]

Brouri, R.

F. Grosshans, G. V. Assche, J. Wenger, R. Brouri, N. J. Cerf, and P. Grangier, "Quantum key distribution using gaussian-modulated coherent states," Nature 421, 238-241 (2003).
[CrossRef] [PubMed]

Cerf, N. J.

J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
[CrossRef]

F. Grosshans, G. V. Assche, J. Wenger, R. Brouri, N. J. Cerf, and P. Grangier, "Quantum key distribution using gaussian-modulated coherent states," Nature 421, 238-241 (2003).
[CrossRef] [PubMed]

Curty, M.

M. Curty, M. Lewenstein, and N. Lütkenhaus, "Entanglement as a precondition for secure quantum key distribution," Phys. Rev. Lett. 92, 217903 (2004).
[CrossRef] [PubMed]

Debuisschert, T.

J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
[CrossRef]

Diamanti, E.

J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
[CrossRef]

Dorrer, C.

C. Dorrer, D. Kilper, H. Stuart, G. Raybon, and M. Raymer, "Linear optical sampling," IEEE Photonics Technol. Lett. 15, 1746-1748 (2003).
[CrossRef]

Ekert, A.

A. Ekert, J. Rarity, P. Tapster, and G. Palma, "Practical quantum cryptography based on 2-photon interferometry," Phys. Rev. Lett. 69, 1293-1295 (1992).
[CrossRef] [PubMed]

Elser, D.

D. Elser, T. Bartley, B. Heim, C. Wittmann, D. Sych, and G. Leuchs, "Feasibility of free space quantum key distribution with coherent polarization states," New J. Phys. 11, 045014 (2009).
[CrossRef]

D. Elser, C. Wittmann, U. L. Andersen, O. Glöckl, S. Lorenz, C. Marquardt, and G. Leuchs, "Guided acoustic wave brillouin scattering in photonic crystal fibers," J. Phys. Conf. Ser. 92, 012108 (2007).
[CrossRef]

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N. Gisin, S. Fasel, B. Kraus, H. Zbinden, and G. Ribordy, "Trojan-horse attacks on quantum-key-distribution systems," Phys. Rev. A 73, 022320 (2006).
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J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
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T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
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R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
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J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
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M. Legré, H. Zbinden, and N. Gisin, "Implementation of continuous variable quantum cryptography in optical fibres using a go-&-return configuration," Quantum Inf. Comput. 6, 326-335 (2006).

N. Gisin, S. Fasel, B. Kraus, H. Zbinden, and G. Ribordy, "Trojan-horse attacks on quantum-key-distribution systems," Phys. Rev. A 73, 022320 (2006).
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D. Stucki, N. Gisin, O. Guinnard, G. Ribordy, and H. Zbinden, "Quantum key distribution over 67 km with a plug&play system," New J. Phys. 4, 41 (2002).
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A. Muller, J. Breguet, and N. Gisin, "Experimental demonstration of quantum cryptography using polarized photons in optical-fiber over more than 1 km," Europhys. Lett. 23, 383-388 (1993).
[CrossRef]

Glöckl, O.

D. Elser, C. Wittmann, U. L. Andersen, O. Glöckl, S. Lorenz, C. Marquardt, and G. Leuchs, "Guided acoustic wave brillouin scattering in photonic crystal fibers," J. Phys. Conf. Ser. 92, 012108 (2007).
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J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
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J. Lodewyck and P. Grangier, "Tight bound on the coherent-state quantum key distribution with heterodyne detection," Phys. Rev. A 76, 022332 (2007).
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J. Rigas, O. Gühne, and N. Lütkenhaus, "Entanglement verification for quantum-key-distribution systems with an underlying bipartite qubit-mode structure," Phys. Rev. A 73, 012341-6 (2006).
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D. Stucki, N. Gisin, O. Guinnard, G. Ribordy, and H. Zbinden, "Quantum key distribution over 67 km with a plug&play system," New J. Phys. 4, 41 (2002).
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Harrington, J. W.

D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, "Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 10503 (2007).
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H. Häseler, T. Moroder, and N. Lütkenhaus, "Testing quantum devices: Practical entanglement verification in bipartite optical systems," Phys. Rev. A 77, 032303-11 (2008).
[CrossRef]

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Y. Zhao, M. Heid, J. Rigas, and N. Lütkenhaus, "Asymptotic security of binary modulated continuous-variable quantum key distribution under collective attacks," Phys. Rev. A 79, 012307-14 (2009).
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D. Elser, T. Bartley, B. Heim, C. Wittmann, D. Sych, and G. Leuchs, "Feasibility of free space quantum key distribution with coherent polarization states," New J. Phys. 11, 045014 (2009).
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Hiskett, P. A.

D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, "Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 10503 (2007).
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B. Qi, L. Huang, L. Qian, and H. Lo, "Experimental study on the gaussian-modulated coherent-state quantum key distribution over standard telecommunication fibers," Phys. Rev. A 76, 052323-9 (2007).
[CrossRef]

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D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, "Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 10503 (2007).
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R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
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J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
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C. Dorrer, D. Kilper, H. Stuart, G. Raybon, and M. Raymer, "Linear optical sampling," IEEE Photonics Technol. Lett. 15, 1746-1748 (2003).
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S. Lorenz, N. Korolkova, and G. Leuchs, "Continuous-variable quantum key distribution using polarization encoding and post selection," Appl. Phys. B 79, 273-277 (2004).
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N. Korolkova, G. Leuchs, R. Loudon, T. C. Ralph, and C. Silberhorn, "Polarization squeezing and continuous variable polarization entanglement," Phys. Rev. A 65, 052306 (2002).
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Kraus, B.

N. Gisin, S. Fasel, B. Kraus, H. Zbinden, and G. Ribordy, "Trojan-horse attacks on quantum-key-distribution systems," Phys. Rev. A 73, 022320 (2006).
[CrossRef]

Kurtsiefer, C.

T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
[CrossRef] [PubMed]

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C. Weedbrook, A. M. Lance, W. P. Bowen, T. Symul, T. C. Ralph, and P. K. Lam, "Coherent-state quantum key distribution without random basis switching," Phys. Rev. A 73, 022316-9 (2006).
[CrossRef]

A. M. Lance, T. Symul, V. Sharma, C. Weedbrook, T. C. Ralph, and P. K. Lam, "No-switching quantum key distribution using broadband modulated coherent light," Phys. Rev. Lett. 95, 180503 (2005).
[CrossRef] [PubMed]

Lance, A. M.

C. Weedbrook, A. M. Lance, W. P. Bowen, T. Symul, T. C. Ralph, and P. K. Lam, "Coherent-state quantum key distribution without random basis switching," Phys. Rev. A 73, 022316-9 (2006).
[CrossRef]

A. M. Lance, T. Symul, V. Sharma, C. Weedbrook, T. C. Ralph, and P. K. Lam, "No-switching quantum key distribution using broadband modulated coherent light," Phys. Rev. Lett. 95, 180503 (2005).
[CrossRef] [PubMed]

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M. Legré, H. Zbinden, and N. Gisin, "Implementation of continuous variable quantum cryptography in optical fibres using a go-&-return configuration," Quantum Inf. Comput. 6, 326-335 (2006).

Leonhardt, U.

U. Leonhardt, J. A. Vaccaro, B. Böhmer, and H. Paul, "Canonical and measured phase distributions," Phys. Rev. A 51, 84 (1995).
[CrossRef] [PubMed]

U. Leonhardt and H. Paul, "Realistic optical homodyne measurements and quasi-probability distributions," Phys. Rev. A 48, 4598-4604 (1993).
[CrossRef] [PubMed]

Leuchs, G.

D. Elser, T. Bartley, B. Heim, C. Wittmann, D. Sych, and G. Leuchs, "Feasibility of free space quantum key distribution with coherent polarization states," New J. Phys. 11, 045014 (2009).
[CrossRef]

D. Elser, C. Wittmann, U. L. Andersen, O. Glöckl, S. Lorenz, C. Marquardt, and G. Leuchs, "Guided acoustic wave brillouin scattering in photonic crystal fibers," J. Phys. Conf. Ser. 92, 012108 (2007).
[CrossRef]

S. Lorenz, N. Korolkova, and G. Leuchs, "Continuous-variable quantum key distribution using polarization encoding and post selection," Appl. Phys. B 79, 273-277 (2004).
[CrossRef]

C. Silberhorn, T. C. Ralph, N. Lütkenhaus, and G. Leuchs, "Continuous variable quantum cryptography: Beating the 3 dB loss limit," Phys. Rev. Lett. 89, 167901 (2002).
[CrossRef] [PubMed]

N. Korolkova, G. Leuchs, R. Loudon, T. C. Ralph, and C. Silberhorn, "Polarization squeezing and continuous variable polarization entanglement," Phys. Rev. A 65, 052306 (2002).
[CrossRef]

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M. Curty, M. Lewenstein, and N. Lütkenhaus, "Entanglement as a precondition for secure quantum key distribution," Phys. Rev. Lett. 92, 217903 (2004).
[CrossRef] [PubMed]

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R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
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D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, "Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 10503 (2007).
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S. Pirandola, S. Mancini, S. Lloyd, and S. L. Braunstein, "Continuous-variable quantum cryptography using two-way quantum communication," Nat. Phys. 4, 726-730 (2008).
[CrossRef]

Lo, H.

B. Qi, L. Huang, L. Qian, and H. Lo, "Experimental study on the gaussian-modulated coherent-state quantum key distribution over standard telecommunication fibers," Phys. Rev. A 76, 052323-9 (2007).
[CrossRef]

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Lodewyck, J.

J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
[CrossRef]

J. Lodewyck and P. Grangier, "Tight bound on the coherent-state quantum key distribution with heterodyne detection," Phys. Rev. A 76, 022332 (2007).
[CrossRef]

Lorenz, S.

D. Elser, C. Wittmann, U. L. Andersen, O. Glöckl, S. Lorenz, C. Marquardt, and G. Leuchs, "Guided acoustic wave brillouin scattering in photonic crystal fibers," J. Phys. Conf. Ser. 92, 012108 (2007).
[CrossRef]

S. Lorenz, N. Korolkova, and G. Leuchs, "Continuous-variable quantum key distribution using polarization encoding and post selection," Appl. Phys. B 79, 273-277 (2004).
[CrossRef]

Loudon, R.

N. Korolkova, G. Leuchs, R. Loudon, T. C. Ralph, and C. Silberhorn, "Polarization squeezing and continuous variable polarization entanglement," Phys. Rev. A 65, 052306 (2002).
[CrossRef]

Lütkenhaus, N.

Y. Zhao, M. Heid, J. Rigas, and N. Lütkenhaus, "Asymptotic security of binary modulated continuous-variable quantum key distribution under collective attacks," Phys. Rev. A 79, 012307-14 (2009).
[CrossRef]

H. Häseler, T. Moroder, and N. Lütkenhaus, "Testing quantum devices: Practical entanglement verification in bipartite optical systems," Phys. Rev. A 77, 032303-11 (2008).
[CrossRef]

J. Rigas, O. Gühne, and N. Lütkenhaus, "Entanglement verification for quantum-key-distribution systems with an underlying bipartite qubit-mode structure," Phys. Rev. A 73, 012341-6 (2006).
[CrossRef]

M. Curty, M. Lewenstein, and N. Lütkenhaus, "Entanglement as a precondition for secure quantum key distribution," Phys. Rev. Lett. 92, 217903 (2004).
[CrossRef] [PubMed]

C. Silberhorn, T. C. Ralph, N. Lütkenhaus, and G. Leuchs, "Continuous variable quantum cryptography: Beating the 3 dB loss limit," Phys. Rev. Lett. 89, 167901 (2002).
[CrossRef] [PubMed]

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Mancini, S.

S. Pirandola, S. Mancini, S. Lloyd, and S. L. Braunstein, "Continuous-variable quantum cryptography using two-way quantum communication," Nat. Phys. 4, 726-730 (2008).
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D. Elser, C. Wittmann, U. L. Andersen, O. Glöckl, S. Lorenz, C. Marquardt, and G. Leuchs, "Guided acoustic wave brillouin scattering in photonic crystal fibers," J. Phys. Conf. Ser. 92, 012108 (2007).
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J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
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J. A. Nelder and R. Mead, "A simplex method for function minimization," The Computer Journal 7, 308-313 (1965).

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R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
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Moroder, T.

H. Häseler, T. Moroder, and N. Lütkenhaus, "Testing quantum devices: Practical entanglement verification in bipartite optical systems," Phys. Rev. A 77, 032303-11 (2008).
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Muller, A.

A. Muller, J. Breguet, and N. Gisin, "Experimental demonstration of quantum cryptography using polarized photons in optical-fiber over more than 1 km," Europhys. Lett. 23, 383-388 (1993).
[CrossRef]

Nam, S. W.

D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, "Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 10503 (2007).
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J. A. Nelder and R. Mead, "A simplex method for function minimization," The Computer Journal 7, 308-313 (1965).

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D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, "Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 10503 (2007).
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R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
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A. Ekert, J. Rarity, P. Tapster, and G. Palma, "Practical quantum cryptography based on 2-photon interferometry," Phys. Rev. Lett. 69, 1293-1295 (1992).
[CrossRef] [PubMed]

Paul, H.

U. Leonhardt, J. A. Vaccaro, B. Böhmer, and H. Paul, "Canonical and measured phase distributions," Phys. Rev. A 51, 84 (1995).
[CrossRef] [PubMed]

U. Leonhardt and H. Paul, "Realistic optical homodyne measurements and quasi-probability distributions," Phys. Rev. A 48, 4598-4604 (1993).
[CrossRef] [PubMed]

Perdigues, J.

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
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T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
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Peterson, C. G.

D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, "Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 10503 (2007).
[CrossRef]

Pirandola, S.

S. Pirandola, S. Mancini, S. Lloyd, and S. L. Braunstein, "Continuous-variable quantum cryptography using two-way quantum communication," Nat. Phys. 4, 726-730 (2008).
[CrossRef]

Qi, B.

B. Qi, L. Huang, L. Qian, and H. Lo, "Experimental study on the gaussian-modulated coherent-state quantum key distribution over standard telecommunication fibers," Phys. Rev. A 76, 052323-9 (2007).
[CrossRef]

Qian, L.

B. Qi, L. Huang, L. Qian, and H. Lo, "Experimental study on the gaussian-modulated coherent-state quantum key distribution over standard telecommunication fibers," Phys. Rev. A 76, 052323-9 (2007).
[CrossRef]

Ralph, T. C.

C. Weedbrook, A. M. Lance, W. P. Bowen, T. Symul, T. C. Ralph, and P. K. Lam, "Coherent-state quantum key distribution without random basis switching," Phys. Rev. A 73, 022316-9 (2006).
[CrossRef]

A. M. Lance, T. Symul, V. Sharma, C. Weedbrook, T. C. Ralph, and P. K. Lam, "No-switching quantum key distribution using broadband modulated coherent light," Phys. Rev. Lett. 95, 180503 (2005).
[CrossRef] [PubMed]

N. Korolkova, G. Leuchs, R. Loudon, T. C. Ralph, and C. Silberhorn, "Polarization squeezing and continuous variable polarization entanglement," Phys. Rev. A 65, 052306 (2002).
[CrossRef]

C. Silberhorn, T. C. Ralph, N. Lütkenhaus, and G. Leuchs, "Continuous variable quantum cryptography: Beating the 3 dB loss limit," Phys. Rev. Lett. 89, 167901 (2002).
[CrossRef] [PubMed]

T. C. Ralph, "Continuous variable quantum cryptography," Phys. Rev. A 61, 010303 (1999).
[CrossRef]

Rarity, J.

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
[CrossRef]

A. Ekert, J. Rarity, P. Tapster, and G. Palma, "Practical quantum cryptography based on 2-photon interferometry," Phys. Rev. Lett. 69, 1293-1295 (1992).
[CrossRef] [PubMed]

Rarity, J. G.

T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
[CrossRef] [PubMed]

Raybon, G.

C. Dorrer, D. Kilper, H. Stuart, G. Raybon, and M. Raymer, "Linear optical sampling," IEEE Photonics Technol. Lett. 15, 1746-1748 (2003).
[CrossRef]

Raymer, M.

C. Dorrer, D. Kilper, H. Stuart, G. Raybon, and M. Raymer, "Linear optical sampling," IEEE Photonics Technol. Lett. 15, 1746-1748 (2003).
[CrossRef]

Ribordy, G.

N. Gisin, S. Fasel, B. Kraus, H. Zbinden, and G. Ribordy, "Trojan-horse attacks on quantum-key-distribution systems," Phys. Rev. A 73, 022320 (2006).
[CrossRef]

D. Stucki, N. Gisin, O. Guinnard, G. Ribordy, and H. Zbinden, "Quantum key distribution over 67 km with a plug&play system," New J. Phys. 4, 41 (2002).
[CrossRef]

Rice, P. R.

D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, "Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 10503 (2007).
[CrossRef]

Rigas, J.

Y. Zhao, M. Heid, J. Rigas, and N. Lütkenhaus, "Asymptotic security of binary modulated continuous-variable quantum key distribution under collective attacks," Phys. Rev. A 79, 012307-14 (2009).
[CrossRef]

J. Rigas, O. Gühne, and N. Lütkenhaus, "Entanglement verification for quantum-key-distribution systems with an underlying bipartite qubit-mode structure," Phys. Rev. A 73, 012341-6 (2006).
[CrossRef]

Rosenberg, D.

D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, "Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 10503 (2007).
[CrossRef]

Salvail, L.

C. Bennett, F. Bessette, G. Brassard, L. Salvail, and J. Smolin, "Experimental quantum cryptography," J. Cryptology 5, 3-28 (1992).
[CrossRef]

Scheidl, T.

T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
[CrossRef] [PubMed]

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
[CrossRef]

Schiller, S.

Schmitt-Manderbach, T.

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
[CrossRef]

T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
[CrossRef] [PubMed]

Shannon, C.

C. Shannon, "Communication theory of secrecy systems," Bell Sys. Tech. J. 28, 656-715 (1949).

Shapiro, J.

J. Shapiro and S. Wagner, "Phase and amplitude uncertainties in heterodyne detection," IEEE J. Quantum Electron. 20, 803-813 (1984).
[CrossRef]

Sharma, V.

A. M. Lance, T. Symul, V. Sharma, C. Weedbrook, T. C. Ralph, and P. K. Lam, "No-switching quantum key distribution using broadband modulated coherent light," Phys. Rev. Lett. 95, 180503 (2005).
[CrossRef] [PubMed]

Silberhorn, C.

N. Korolkova, G. Leuchs, R. Loudon, T. C. Ralph, and C. Silberhorn, "Polarization squeezing and continuous variable polarization entanglement," Phys. Rev. A 65, 052306 (2002).
[CrossRef]

C. Silberhorn, T. C. Ralph, N. Lütkenhaus, and G. Leuchs, "Continuous variable quantum cryptography: Beating the 3 dB loss limit," Phys. Rev. Lett. 89, 167901 (2002).
[CrossRef] [PubMed]

Smolin, J.

C. Bennett, F. Bessette, G. Brassard, L. Salvail, and J. Smolin, "Experimental quantum cryptography," J. Cryptology 5, 3-28 (1992).
[CrossRef]

Sodnik, Z.

T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
[CrossRef] [PubMed]

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
[CrossRef]

Stenholm, S.

S. Stenholm, "Simultaneous measurement of conjugate variables," Ann. Phys. 218, 233-254 (1992).
[CrossRef]

Stuart, H.

C. Dorrer, D. Kilper, H. Stuart, G. Raybon, and M. Raymer, "Linear optical sampling," IEEE Photonics Technol. Lett. 15, 1746-1748 (2003).
[CrossRef]

Stucki, D.

D. Stucki, N. Gisin, O. Guinnard, G. Ribordy, and H. Zbinden, "Quantum key distribution over 67 km with a plug&play system," New J. Phys. 4, 41 (2002).
[CrossRef]

Sych, D.

D. Elser, T. Bartley, B. Heim, C. Wittmann, D. Sych, and G. Leuchs, "Feasibility of free space quantum key distribution with coherent polarization states," New J. Phys. 11, 045014 (2009).
[CrossRef]

Symul, T.

C. Weedbrook, A. M. Lance, W. P. Bowen, T. Symul, T. C. Ralph, and P. K. Lam, "Coherent-state quantum key distribution without random basis switching," Phys. Rev. A 73, 022316-9 (2006).
[CrossRef]

A. M. Lance, T. Symul, V. Sharma, C. Weedbrook, T. C. Ralph, and P. K. Lam, "No-switching quantum key distribution using broadband modulated coherent light," Phys. Rev. Lett. 95, 180503 (2005).
[CrossRef] [PubMed]

Tapster, P.

A. Ekert, J. Rarity, P. Tapster, and G. Palma, "Practical quantum cryptography based on 2-photon interferometry," Phys. Rev. Lett. 69, 1293-1295 (1992).
[CrossRef] [PubMed]

Tiefenbacher, F.

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
[CrossRef]

T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
[CrossRef] [PubMed]

Trojek, P.

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
[CrossRef]

Tualle-Brouri, R.

J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
[CrossRef]

Ursin, R.

T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
[CrossRef] [PubMed]

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
[CrossRef]

Vaccaro, J. A.

U. Leonhardt, J. A. Vaccaro, B. Böhmer, and H. Paul, "Canonical and measured phase distributions," Phys. Rev. A 51, 84 (1995).
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Vernam, G.

G. Vernam, "Cipher printing telegraph systems for secret wire and radio telegraphic communications," J. Amer. Inst. Elect. Eng., 109 (1926).

Wagner, S.

J. Shapiro and S. Wagner, "Phase and amplitude uncertainties in heterodyne detection," IEEE J. Quantum Electron. 20, 803-813 (1984).
[CrossRef]

Weedbrook, C.

C. Weedbrook, A. M. Lance, W. P. Bowen, T. Symul, T. C. Ralph, and P. K. Lam, "Coherent-state quantum key distribution without random basis switching," Phys. Rev. A 73, 022316-9 (2006).
[CrossRef]

A. M. Lance, T. Symul, V. Sharma, C. Weedbrook, T. C. Ralph, and P. K. Lam, "No-switching quantum key distribution using broadband modulated coherent light," Phys. Rev. Lett. 95, 180503 (2005).
[CrossRef] [PubMed]

Weier, H.

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
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T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
[CrossRef] [PubMed]

Weinfurter, H.

T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
[CrossRef] [PubMed]

R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
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Wenger, J.

F. Grosshans, G. V. Assche, J. Wenger, R. Brouri, N. J. Cerf, and P. Grangier, "Quantum key distribution using gaussian-modulated coherent states," Nature 421, 238-241 (2003).
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Wittmann, C.

D. Elser, T. Bartley, B. Heim, C. Wittmann, D. Sych, and G. Leuchs, "Feasibility of free space quantum key distribution with coherent polarization states," New J. Phys. 11, 045014 (2009).
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D. Elser, C. Wittmann, U. L. Andersen, O. Glöckl, S. Lorenz, C. Marquardt, and G. Leuchs, "Guided acoustic wave brillouin scattering in photonic crystal fibers," J. Phys. Conf. Ser. 92, 012108 (2007).
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Zbinden, H.

M. Legré, H. Zbinden, and N. Gisin, "Implementation of continuous variable quantum cryptography in optical fibres using a go-&-return configuration," Quantum Inf. Comput. 6, 326-335 (2006).

N. Gisin, S. Fasel, B. Kraus, H. Zbinden, and G. Ribordy, "Trojan-horse attacks on quantum-key-distribution systems," Phys. Rev. A 73, 022320 (2006).
[CrossRef]

D. Stucki, N. Gisin, O. Guinnard, G. Ribordy, and H. Zbinden, "Quantum key distribution over 67 km with a plug&play system," New J. Phys. 4, 41 (2002).
[CrossRef]

Zeilinger, A.

T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
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R. Ursin, F. Tiefenbacher, T. Schmitt-Manderbach, H. Weier, T. Scheidl, M. Lindenthal, B. Blauensteiner, T. Jennewein, J. Perdigues, P. Trojek, B. Ömer, M. Fürst, M. Meyenburg, J. Rarity, Z. Sodnik, C. Barbieri, H. Weinfurter, and A. Zeilinger, "Entanglement-based quantum communication over 144km," Nat. Phys. 3, 481-486 (2007).
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Zhao, Y.

Y. Zhao, M. Heid, J. Rigas, and N. Lütkenhaus, "Asymptotic security of binary modulated continuous-variable quantum key distribution under collective attacks," Phys. Rev. A 79, 012307-14 (2009).
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S. Stenholm, "Simultaneous measurement of conjugate variables," Ann. Phys. 218, 233-254 (1992).
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Appl. Phys. B (1)

S. Lorenz, N. Korolkova, and G. Leuchs, "Continuous-variable quantum key distribution using polarization encoding and post selection," Appl. Phys. B 79, 273-277 (2004).
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C. Shannon, "Communication theory of secrecy systems," Bell Sys. Tech. J. 28, 656-715 (1949).

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IEEE Photonics Technol. Lett. (1)

C. Dorrer, D. Kilper, H. Stuart, G. Raybon, and M. Raymer, "Linear optical sampling," IEEE Photonics Technol. Lett. 15, 1746-1748 (2003).
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J. Amer. Inst. Elect. Eng. (1)

G. Vernam, "Cipher printing telegraph systems for secret wire and radio telegraphic communications," J. Amer. Inst. Elect. Eng., 109 (1926).

J. Cryptology (1)

C. Bennett, F. Bessette, G. Brassard, L. Salvail, and J. Smolin, "Experimental quantum cryptography," J. Cryptology 5, 3-28 (1992).
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J. Phys. Conf. Ser. (1)

D. Elser, C. Wittmann, U. L. Andersen, O. Glöckl, S. Lorenz, C. Marquardt, and G. Leuchs, "Guided acoustic wave brillouin scattering in photonic crystal fibers," J. Phys. Conf. Ser. 92, 012108 (2007).
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Nature (1)

F. Grosshans, G. V. Assche, J. Wenger, R. Brouri, N. J. Cerf, and P. Grangier, "Quantum key distribution using gaussian-modulated coherent states," Nature 421, 238-241 (2003).
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New J. Phys. (2)

D. Stucki, N. Gisin, O. Guinnard, G. Ribordy, and H. Zbinden, "Quantum key distribution over 67 km with a plug&play system," New J. Phys. 4, 41 (2002).
[CrossRef]

D. Elser, T. Bartley, B. Heim, C. Wittmann, D. Sych, and G. Leuchs, "Feasibility of free space quantum key distribution with coherent polarization states," New J. Phys. 11, 045014 (2009).
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Phys. Rev. A (12)

J. Lodewyck, M. Bloch, R. Garcia-Patron, S. Fossier, E. Karpov, E. Diamanti, T. Debuisschert, N. J. Cerf, R. Tualle-Brouri, S. W. McLaughlin, and P. Grangier, "Quantum key distribution over 25 km with an all-fiber continuous-variable system," Phys. Rev. A 76, 042305-10 (2007).
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[CrossRef]

C. Weedbrook, A. M. Lance, W. P. Bowen, T. Symul, T. C. Ralph, and P. K. Lam, "Coherent-state quantum key distribution without random basis switching," Phys. Rev. A 73, 022316-9 (2006).
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J. Lodewyck and P. Grangier, "Tight bound on the coherent-state quantum key distribution with heterodyne detection," Phys. Rev. A 76, 022332 (2007).
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N. Korolkova, G. Leuchs, R. Loudon, T. C. Ralph, and C. Silberhorn, "Polarization squeezing and continuous variable polarization entanglement," Phys. Rev. A 65, 052306 (2002).
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H. Häseler, T. Moroder, and N. Lütkenhaus, "Testing quantum devices: Practical entanglement verification in bipartite optical systems," Phys. Rev. A 77, 032303-11 (2008).
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Y. Zhao, M. Heid, J. Rigas, and N. Lütkenhaus, "Asymptotic security of binary modulated continuous-variable quantum key distribution under collective attacks," Phys. Rev. A 79, 012307-14 (2009).
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U. Leonhardt, J. A. Vaccaro, B. Böhmer, and H. Paul, "Canonical and measured phase distributions," Phys. Rev. A 51, 84 (1995).
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J. Rigas, O. Gühne, and N. Lütkenhaus, "Entanglement verification for quantum-key-distribution systems with an underlying bipartite qubit-mode structure," Phys. Rev. A 73, 012341-6 (2006).
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[CrossRef] [PubMed]

C. Silberhorn, T. C. Ralph, N. Lütkenhaus, and G. Leuchs, "Continuous variable quantum cryptography: Beating the 3 dB loss limit," Phys. Rev. Lett. 89, 167901 (2002).
[CrossRef] [PubMed]

D. Rosenberg, J. W. Harrington, P. R. Rice, P. A. Hiskett, C. G. Peterson, R. J. Hughes, A. E. Lita, S. W. Nam, and J. E. Nordholt, "Long-distance decoy-state quantum key distribution in optical fiber," Phys. Rev. Lett. 98, 10503 (2007).
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T. Schmitt-Manderbach, H. Weier, M. Fürst, R. Ursin, F. Tiefenbacher, T. Scheidl, J. Perdigues, Z. Sodnik, C. Kurtsiefer, J. G. Rarity, A. Zeilinger, and H. Weinfurter, "Experimental demonstration of free-space decoystate quantum key distribution over 144 km," Phys. Rev. Lett. 98, 010504 (2007).
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A. Ekert, J. Rarity, P. Tapster, and G. Palma, "Practical quantum cryptography based on 2-photon interferometry," Phys. Rev. Lett. 69, 1293-1295 (1992).
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Quantum Inf. Comput. (1)

M. Legré, H. Zbinden, and N. Gisin, "Implementation of continuous variable quantum cryptography in optical fibres using a go-&-return configuration," Quantum Inf. Comput. 6, 326-335 (2006).

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Figures (5)

Fig. 1.
Fig. 1.

(left) Schematics of the QKD setup, (right) the detection part is a random phase heterodyne detection using the polarization degree of freedom. Our scheme is similar to a technique called linear optical sampling [27]. In contrast to their system, we have a shot noise limited detection and a SNR improvement of about 40 dB.

Fig. 2.
Fig. 2.

Curves show lower bounds for quantum correlations. The variance of the Stokes operators is normalized by the local oscillator intensity resulting in the normalized variance Var(Ŝ 2,3)/〈 LO〉. The different curves correspond to different channel transmissions η. Effective entanglement is verified in the shaded areas.

Fig. 3.
Fig. 3.

(a) Lissajous figure of a phase randomized signal is measured for different settings of the QWP in the setup. If the measured quadratures Xψ and Xϕ are not orthogonal, the shape of the graph will be elliptical. We demonstrate that orthogonal quadratures are measured for the correct QWP angle (orange trace). (b) The phase is estimated from blocks of calibration pulses. The figure shows the standard deviation of the phase drift between different calibration blocks.

Fig. 4.
Fig. 4.

Alice and Bob are connected back to back. (a) Combined Q-function generated from 5 million pulses with amplitudes αS = 0.5 (b) Q-functions for each signal state. (c) Excess noise estimated from Q-function for varying signal amplitudes. (d) Average excess noise (circles) compared to the bounds given by the entanglement criterion (solid line), shown with the 3-sigma confidentiality interval (dashed lines).

Fig. 5.
Fig. 5.

Alice and Bob are connected with a 2 km optical fiber. (a) Excess noise estimated from Q-function measurement for varying signal amplitudes. (b) Average excess noise (circles) compared to the bounds given by the entanglement criterion (solid line), shown with the 3-sigma confidentiality interval (dashed lines).

Equations (19)

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Ψ AB = 1 2 ( 0 A α B + 1 A α B ) .
S ̂ 1 = α ̂ LO α ̂ LO α ̂ S α ̂ S = n ̂ LO n ̂ s
S ̂ 2 = α ̂ LO α ̂ S + α ̂ S α ̂ LO
S ̂ 3 = i ( α ̂ S α ̂ LO α ̂ LO α ̂ S ) .
χ ( ρ AB ) = [ 0 0 B ρ AB 0 1 B ρ AB 1 0 B ρ AB 1 1 B ρ AB ]
B = [ 1 ̂ B S ̂ 2 S ̂ 3 S ̂ 2 S ̂ 2 2 S ̂ 2 S ̂ 3 S ̂ 3 S ̂ 3 S ̂ 2 S ̂ 3 2 ] .
χ ( ρ AB ) T A 0 ,
S ̂ 2 2 + S ̂ 3 2 = 2 ( S ̂ 0 + 2 n ̂ LO n ̂ s ) ,
n ̂ s = 1 2 ( S ̂ 0 S ̂ 1 ) ,
S ̂ 1 = S ̂ 0 ( 1 + 1 n ̂ LO ) S ̂ 2 2 + S ̂ 3 2 2 n ̂ LO .
S ̂ 1 1 + n ̂ LO S ̂ 2 2 + S ̂ 3 2 2 n ̂ LO .
n ̂ HD 1 = 1 2 ( ( a ̂ LO e i ϕ I + a ̂ LO e i ϕ I ) ( a ̂ S + a ̂ S )
+ ( a ̂ S + a ̂ S ) ( a ̂ LO e i ϕ I + a ̂ LO e i ϕ I ) )
= α LO ( cos ( ϕ I ) α + δ X ̂ S , ϕ I + δ X ̂ S ) ,
n ̂ HD 2 = 1 2 ( ( a ̂ LO e i ϕ I + π 2 a ̂ LO e i ϕ I + π 2 ) ( a ̂ S a ̂ S )
+ ( a ̂ S a ̂ S ) ( a ̂ LO e i ϕ I + π 2 a ̂ LO e i ϕ I + π 2 ) )
= α LO ( cos ( ϕ I + π 2 ) α + δ X ̂ S , ϕ I + π 2 + δ X ̂ S ) .
S ̂ 2 2 n ̂ LO + S ̂ 3 2 n ̂ LO γ LO γ S 2 2 max ( u ̂ S 2 2 u ̂ LO ) + γ LO γ S 3 2 max ( u ̂ S 3 2 u ̂ LO ) ,
γ LO γ s i 2 Δ 2 u ̂ S i , snl u ̂ LO , snl = Δ 2 S ̂ i , snl n ̂ LO , snl = 1 .

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