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APS » Journals » Phys. Rev. Lett. » Volume 85 » Issue 6
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Phys. Rev. Lett. 85, 1330–1333 (2000)

Limitations on Practical Quantum Cryptography

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Gilles Brassard1, Norbert Lütkenhaus2, Tal Mor3,4, and Barry C. Sanders5
1Département IRO, Université de Montréal, C.P. 6128, succursale centre-ville, Montréal, Québec Canada H3C 3J7
2Helsinki Institute of Physics, P.O. Box 9, 00014 Helsingin yliopisto, Finland
3Electrical Engineering, University of California at Los Angeles, Los Angeles, California 90095-1594
4Electrical Engineering, College of Judea and Samaria, Ariel, Israel
5Department of Physics, Macquarie University, Sydney, New South Wales 2109, Australia

Received 2 February 2000; published in the issue dated 7 August 2000

We provide limits to practical quantum key distribution, taking into account channel losses, a realistic detection process, and imperfections in the “qubits” sent from the sender to the receiver. As we show, even quantum key distribution with perfect qubits might not be achievable over long distances when the other imperfections are taken into account. Furthermore, existing experimental schemes (based on weak pulses) currently do not offer unconditional security for the reported distances and signal strength. Finally we show that parametric down-conversion offers enhanced performance compared to its weak coherent pulse counterpart.

© 2000 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.85.1330
DOI:
10.1103/PhysRevLett.85.1330
PACS:
03.67.Dd, 05.40.Ca, 42.50.Dv, 89.80.+h
 
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