Decoy States and Low-Density Parity-Check Error-Correcting Codes in Quantum Cryptography with Phase–Time Coding

Abstract

The cryptographic robustness of quantum key distribution (QKD) with phase–time coding against a photon number splitting (PNS) attack is analyzed. The line length up to which a secret key distribution is guaranteed is determined both by the protocol itself and by the efficiency of error correction in raw keys. The effect of different parameters of avalanche single-photon detectors on the length of the secret key distribution line is investigated. To correct errors, various versions of low-density parity-check (LDPC) codes are considered whose efficiency today is the closest to the Shannon theoretical limit.