Quantum Key Distribution Protocols And Measurement Of Disorder In Binary Sequences

Quantum key distribution(QKD) is developed based on quantum theory. It has two basic characteristics, i.e., the eavesdropping detectability and unconditional security. In principle, it is an undeciphered cryptosystem. Therefore, it draws much attention of cryptographers and physical scientists. There are many excting developments in theory, experiments and applications. Now it becomes a new hot point.In this paper, we carry out the research on three interesting problems in QKD. First, considering the low utilization rate of photons and the disability of authentication in BB84 protocol, we propose a QKD protocol based on BB84 protocol and challenge-response mechanism. In this protocol, Alice uses the Hash function and classical sequences, including challenge information and the keys, to prepare the photons according to that in BB84 protocol. Bob sends response information to Alice after he measures the photons according to Hash function and the measurement results. Alice checks the error rate and decides whether to use the key or not. Ideally, the utilization rate of photons is almost 100%. The security of the protocol is similar as that of the BB84 protocol. Furthermore, it also provides authentication.Then, we propose a novel error reconciliation protocol in combination with the classical one-time pad mechanism. In the protocol, Alice sends classical one-time challenge information and the corresponding position information in the raw key squence to Bob. Bob corrects errors using the information he has received. There is no need to directly exchange the information of the key. Comparing with existing QKD protocols, it can highly increase quantum key generation rates.At last, a binary sequence is obtained after QKD and the sequence is best to be a random sequence or an approximate random ones. We find a novel way to measure the degree of disorder of binary sequences based on the many-body localization theory in condensed matter physics and the diffraction theory for complex gratings. It provides a quantitative measurement disorder of arbitrary binary sequences.