Theoretical And Experimental Study Of Quantum Digital Signature Based On Heralded Single-photon Sources

Cryptography is the study of how to transmit information confidentially.The security of traditional cryptography is designed with computational complexity.Digital signature is one of the traditional cryptography systems,which is widely used in financial,email and other communication tasks.But with the continuous breakthrough of algorithms and the booming development of quantum computers,traditional cryptography is no longer secure.Quantum cryptography provides a promising alternative solution,it does not depend on mathematical difficulty,but the laws of physics to provide unconditional security of information in theory.As an important part of quantum cryptography,quantum digital signature can theoretically realize unconditional and secure certification.Since the requirement of secure quantum channel in quantum digital signature scheme is removed,quantum digital signature started to be practical from theoretical analysis to experimental verification.How to improve the system performance and speed up the process of practical application has also become the focus of current research.In order to improve the actual system performance of quantum digital signature,the following three works are done:1.According to the previous quantum digital signature using three intensities and the heralded single photon source,we report a proof-of-principle demonstration for the first time.We set up the experimental platform and measure the system parameters to simulate the signature rate under the condition of security level of 10^-5 and optimizing variable parameters.Then we run the system with attenuation channels equivalent to optical fibers of 50 km and 100 km transmission distances,and get corresponding signature rates.The experimental results match well with the theoretical predictions,demonstrating correctness of the scheme.2.Considering to improve the signature rate further,we propose a quantum digital signature scheme with four intensities and biased basis,which has more parameters to optimize and more kinds of events,so as to estimate the channel parameters more tightly.We also simulate the signature rate with the global parameter optimization algorithm and show the comparison of four-intensity scheme and three-intensity scheme.3.Considering theoretical advantages of the four-intensity decoy-state scheme,we use the same experimental platform to simulate the signature rate under the condition of security level of 10^-5 and optimizing all variable parameters.Then we run the system with attenuation channels equivalent to optical fibers of 50 km and 100 km transmission distances,and get corresponding signature rates.The experimental results agree well with the theoretical predictions,verifying correctness of the scheme.