We propose a modified version of the Bennett–Brassard 1984 quantum key distribution protocol intended to tolerate losses, certain forms of noise, and the so-called photon-number splitting attack. These are the issues facing the realization of practical quantum key distribution. The modified protocol is based on quantum non-demolition measurements for systems using weak coherent pulses. Our scheme ensures that emissions corresponding to zero photon pulses, multi-photon pulses, and detector double-clicks are discarded before sifting to improve sifting efficiency and increase the secret key rate. Moreover, we perform the finite key analysis to obtain the maximal achievable secret-key fraction and the corresponding optimal number of signals. Also, we compare our proposed protocol to the decoy-state quantum key distribution protocol. We observe that our proposed quantum key distribution scheme enables a more extended transmission distance than the decoy-state quantum key distribution protocol. Thus, this an advance in quantum communication because current limitations on quantum key distribution involve transmitting secret keys over more considerable distances in the presence of noise or losses in optical fibres.
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