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Journal of Optoelectronics·laser

Application of FPGA-based SER/DES for quantum cryptography

Hong Zhang

Published Jan 1, 2010• 0 citations
OpenAlex

Abstract

At the long-distance quantum key distribution(QKD) experiments,high-speed quantum transmission is needed.In this paper,quantum transmission rate at 500 Mbit/s is fulfilled based on SER/DES module inside FPGA,and a time synchronization design between transmitter and receiver using a low frequency sync-pulse(2 MHz) is proposed.For the experiment′s requirements,signal discriminator,pseudo-random number generator,time synchronization and data coding are developed.This design has been applied successfully to build decoy-state based long-distance QKD experiment.

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At the long-distance quantum key distribution(QKD) experiments,high-speed quantum transmission is needed.In this paper,quantum transmission rate at 500 Mbit/s is fulfilled based on SER/DES module inside FPGA,and a time synchronization design between transmitter and receiver using a low frequency sync-pulse(2 MHz) is proposed.For the experiment′s requirements,signal discriminator,pseudo-random number generator,time synchronization and data coding are developed.This design has been applied successfully to build decoy-state based long-distance QKD experiment.
A light synchronization scheme to solve the key problem of signal synchronization in quantum key distribution(QKD)system is proposed.At side of the transmitter,the field-programmable gate array (FPGA)chip produces a synchronization pulse sequence of certain pattern.The pulse sequence drives laser to transmit sync light through one fiber along with signal light to the receiver.The sync light reverts to sync pulse sequence through fast discrimination at side of the receiver,and the pulses are provided to the single-photon detector as gate after high-precision delay adjustment.Simultaneously,the receiver uses a high-frequency clock to sample the sync pulse sequence in FPGA for encoding,synchronizing the transmitter and receiver.The scheme has a high-precision,low-cost,high fault tolerance feature,and was successfully applied to metro quantum communication network.
A real-time quantum key distribution (QKD) system is developed in this paper. In the system, based on the feature of a field-programmable gate array, secure key extraction control and algorithm have been optimally designed to perform sifting, error correction, and privacy amplification altogether in real time. In the QKD experiment, information synchronization mechanism and high-speed classic data channel are designed to ensure the steady operation of the system. Decoy state and synchronous laser light source are used in the system, while the length of optical fiber between Alice and Bob is 20 km. With photons repetition frequency of 20 MHz, the final key rate could reach 17 kb/s. Smooth and robust operation is verified with 6 h continuous test and associated with encrypted voice communication test.
We report an implementation of decoy-state quantum key distribution (QKD) over 200 km optical fiber cable through photon polarization encoding. This is achieved by constructing the whole QKD system operating at 320 MHz repetition rate, and developing high-speed transmitter and receiver modules. A novel and economic way of synchronization method is designed and incorporated into the system, which allows to work at a low frequency of 40kHz and removes the use of highly precise clock. A final key rate of 15 Hz is distributed within the experimental time of 3089 seconds, by using super-conducting single photon detectors. This is longest decoy-state QKD yet demonstrated up to date. It helps to make a significant step towards practical secure communication in long-distance scope.
The development of quantum computer technology has brought unprecedented threats to traditional cryptography methods. So far, the combination of Quantum Key Distribution (QKD) and one-time pad cryptography is the best solution to overcome the problem since it makes provable information-theoretic secure encryption possible. While the final key generation rate of most QKD systems cannot meet the needs of practical applications. One of the important reasons is the unsatisfied performance of communication scheme of classical channel in the QKD post processing system (QKDPPS). In this paper, an efficient FPGA-based communication scheme of classical channel in high speed QKD system is presented. Considering the following features of high transmission speed, multiple data types, large data quantity and strict data sequence of the communication over classical channel in a high-speed QKD system, the optical fiber is chosen as the communication medium and a high performance transmission protocol suitable for QKD is designed, including the packeting strategy based on data exchange rate and a reliability assurance scheme on the data link layer. The experimental results demonstrate that our communication scheme can provide stable communication service at 1.66 Gbps for a high-speed QKD system.
Quantum key distribution (QKD) is the most matured application of quantum communication. The time synchronization and system timing jitter are essential to a practical QKD experiment, which can directly influence the quantum bit error rate (QBER) and the final key rate. High precision time-to-digital converters (TDCs) can effectively reduce the system timing jitter, resulting in lower QBER and higher key rate. Here, we introduce a TDC based on a field programmable gate array (FPGA). Its high resolution (LSB) of 50 ps with precision (RMS) less than 50 ps, low dead time and large dynamic range can well meet the requirement of the QKD experiment. A free space QKD system setup using the FPGA-based TDC has been assembled. The timing precision of the synchronous light and the system timing jitter were determined. The results demonstrate that the FPGA-based TDC could be successfully applied in the QKD experiment.
Time synchronization is a crucial requirement in quantum key distribution (QKD)8 protocols, ensuring accurate key generation via the correct assignment of bits of raw key and9 enabling eavesdropping detection via the precise recording of photon statistics. State-of-the-art10 experiments typically use an extra channel to synchronize the clocks of the transmitter and receiver11 via classical signals. In this work, we study the possibility of performing clock synchronization12 via the signals used for the key generation, which are already present in decoy-state-based BB8413 protocols.14 Without altering the protocol in any way, we use the different mean photon numbers of the15 signal and decoy states for time synchronization without a dedicated physical channel capable of16 clock synchronization. The proposed method relies only on the photons sent and received for17 key generation and does not require any change to the QKD protocol. The only change in the18 experiment is on the software level, thus making it very simple to implement.19 We demonstrate clock synchronization method in a simulation of a specific fiber-based QKD20 experiment. Like other decoy-state-based BB84 protocols, it is based on weak coherent pulses.21 In this simulation, we investigate the parameter space to find limits and optimal choices of our22 proposed method.23 In addition to the non-protocol-altering clock synchronization method, we also discuss an24 approach that significantly improves performance in lossy channels by introducing an additional25 decoy state with a very high mean photon number.26 By eliminating the need for an extra channel capable of clock synchronization, both methods27 proposed potentially reduce the complexity and cost of QKD systems and improve their agility