Application Of FPGA Based Data Acquisition System In Quantum Key Distribution

Cryptography is an ancient applied science that has a wide range of applications and influences in diplomacy,military,and people's daily lives.With the rapid development of information technology,the amount of information circulation has climbed to an unprecedented height,and urgent demands the security of information have also been raised.Information security is not only about personal privacy,social fairness,but also about personal property security and even personal safety.With the rapid development of the economy,the rapid advancement of basic science and engineering,the demand for practical and secure cryptosystems is constantly evolving and changing.In recent years,with the development of electronic computer technology,especially the introduction of quantum computers and corresponding quantum algorithms,the security of traditional encryption algorithms that rely on computational complexity has been seriously challenged.The superior parallel processing power of quantum computing will invalidate some current cryptosystems,forcing people to seek new and absolutely secure cryptosystems and provide a powerful guarantee for information security in a practical engineering implementation.Quantum cryptography is a product of the ingenious combination of quantum mechanics and cryptography.It can realize the distribution of keys in an insecure common channel under the framework of quantum mechanics theory,and combines the one-time cryptosystem to achieve unconditional security perfectly.Quantum key distribution has been receiving much attention since its introduction in 1984.After more than 30 years of development,great progress has been made in both theory and experiment,and it has been continuously promoted to practical and industrialization.The practical application of quantum key distribution is inseparable from the combination of basic science and engineering.Basic science provides theoretical basis and safety proof for the realization of quantum key distribution,and engineering is a powerful tool for practical application of theory.Engineering uses existing software and hardware conditions to build a bridge between theory and practical application,and continuously improve the scale of quantum key distribution and commercialization.This article describes some of the author's work during the master's degree,the main content is to build an FPGA-based unit for experimental control that can be applied to quantum key distribution.The content mainly includes the following aspects:1.Establish the Nanjing University Inter-University Quantum Communication Optical Network,measure,analyze and improve the network.2.Based on the LSFR algorithm,using an FPGA to generate a random number sequence with a rate of 200 MHz,and generating a nanosecond narrow pulse signal for modulating the laser according to the random number,using the pulse to modulate the optical pulse sequence for information encoding.3.Realize clock synchronization between the transmitting end and the receiving end:use the photoelectric conversion component to transmit the clock information used by the transmitting end system to the receiving end system,and use the phase locked loop circuit to recover the clock signal to generate the clock frequency required for the system to work.4.Simultaneous acquisition of single photon signal:The superconducting nanowire single photon detector is used to detect the weak coherent pulse,and the output electrical signal is processed by the subsequent circuit and then connected to the receiving end system for acquisition.The signal sequence collected by the receiving end is compared with the signal sequence transmitted by the transmitting end to analyze the bit error rate of the system.The data acquisition system designed and implemented in this paper has passed the offline test of the inter-school quantum communication network,which realizes the normal operation of the function and will help to develop in the direction of practical use.