ua nt - p h / 01 01 09 8 v 2 18 S ep 2 00 1 Quantum cryptography

II A beautiful idea 2 A The intuition . . . . . . . . . . . . . . . 2 B Classical cryptography . . . . . . . . . 3 1 Asymmetrical (public-key) cryptosystems . . . . . . . . . . . . . . . 3 2 Symmetrical (secret-key) cryptosystems . . . . . . . . . . . . . . . . . 4 3 The one-time-pad as “classical teleportation” . . . . . . . . . . . . . . 5 C The example of the BB84 protocol . . . 5 1 Principle . . . . . . . . . . . . . . . 5 2 No cloning theorem . . . . . . . . . 6 3 Intercept-resend strategy . . . . . . 6 4 Error correction, privacy amplification and quantum secret growing . . 6 5 Advantage distillation . . . . . . . . 8 D Other protocols . . . . . . . . . . . . . 8 1 2-state protocol . . . . . . . . . . . 8 2 6-state protocol . . . . . . . . . . . 9 3 EPR protocol . . . . . . . . . . . . 9 4 Other variations . . . . . . . . . . . 10 E Quantum teleportation as “Quantum one-time-pad” . . . . . . . . . . . . . . 10 F Optical amplification, quantum nondemolition measurements and optimal quantum cloning . . . . . . . . . . . . . 10