Research On Decoy State Quantum Key Distribution Protocol

The most peculiar characteristics of quantum mechanics are the existence of indivisible quanta and of entangled systems. Both of these lie at the root of quantum key distribution (QKD) which could very well be the first commercial application of quantum physics at the single quantum level. QKD can offer efficient cryptographic systems providing an unprecedented level of security which can in principle be guaranteed without putting any restriction on an eavesdropper's power. QKD can be used for diplomatic, military, financial and other areas required a high degree of confidentiality which expected to be the main next-generation encryption.Decoy state scheme has been proven to be a very useful method for significantly enhancing the performance of QKD systems with practical light sources. People have done a lot of research work in the field of decoy state last five years, but there are still many issues worthy of further study. This dissertation exactly focuses on the theoretical study of practical decoy state protocol, and our target is to accelerate the practical application of QKD. The main contents are shown as follows:1. We study the general decoy state protocol based on heralded single-photon source (HSPS). We have carried out a derivation of the formula and numerical simulation respectively in the active scheme which the distribution is Thermal or Poisson, and so in passive scheme.2. We discuss the practical active and passive decoy state protocol based on HSPS. In the active scenario, we use the date of two decoy-states plus the vacuum state to estimate the value of the single photon count rate and error rate. While in passive scenario, through the post selection of the detector response, the optical pulse is divided into 0, 1 and the other three types of subset to be implement the decoy state scheme. 3. We consider the situation which an available photon number resolving detector placed at the receiver side. We propose an active and passive scheme. In active scheme, we use the same two decoy state plus vacuum state protocol, and in passive scheme, through the response detector, the signal pulse is divided into 1 and 2 two type of subset to carry out the decoy state protocol.