Limitations on Practical Quantum Cryptography

Gilles Brassard; Norbert Lütkenhaus; Tal Mor; Barry C. Sanders

doi:10.1103/PhysRevLett.85.1330

Limitations on Practical Quantum Cryptography

Gilles Brassard, Norbert Lütkenhaus, Tal Mor, and Barry C. Sanders

Phys. Rev. Lett. 85, 1330 – Published 7 August 2000

Abstract

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.

Received 2 February 2000

DOI:https://doi.org/10.1103/PhysRevLett.85.1330

Authors & Affiliations

Gilles Brassard¹, Norbert Lütkenhaus², Tal Mor^3,4, 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