Quantum cryptography with and without entanglement

Abstract

Quantum cryptography is reviewed, first using entanglement both for the intuition and for the experimental realizations. Next, the implementation is simplified in several steps until it becomes practical. At this point entanglement has disappeared. This method can be seen as a lesson of Applied Physics. Finally, security issues, e.g. photon number splitting attacks, and counter-measures are discussed.

8 pages, 8 figures, Proceedings for Les Houches Summer School on "Quantum entanglement and information processing", june-july 2003