Theoretical Study On Decoy State Quantum Key Distribution

Quantum key distribution which combines perfectly quantum mechanics with cryptography can provide unconditional security key between two remote parties and be applied in many fields, such as military, diplomacy, commerce. With the rapid development of theoretical study and experimental technology in the past twenty years, it has begun to be applied in real world. It is believed that quantum key distribution will play an important role in the future information science.This dissertation is focus on the theoretical study of practical quantum key distribution system, and our goal is to accelerate the commercial application of quantum key distribution. The main contents are follows:We first propose a decoy state quantum key distribution with odd coherent state. Comparing with other schemes, the numerical calculations show that our scheme can improve efficiently the key generation rate and secure communication distance. Furthermore, only one decoy state is necessary to approach to the perfect asymptotic limit with infinite decoy states in our scheme, but at least two decoy states are needed in other scheme.Finally, we consider the practical decoy state QKD with finite resource for the coherent state and obtain the lower bound of the key rate. The numerical calculations show that when the length of exchanged bit is taken into account, both the key rate and maximal communication distance are lower than the results of asymptotic scenario. And the relative deviation of the key rate for the two scenarios will increase quickly with the increase of the communication distance.