This paper discusses in detail the principle of the optical devices in both continuous and discrete variable quantum key distribution,including the classical QKD communication system. A circuit control module using Xilinx Corporation's ML405 Evaluation Platform and suitable for various QKD experiments is proposed. The controller generates necessary nanosecond clock signals for optical devices and integrates quantum cryptography communication system. Finally,the design flow is implemented by downloading the bit stream,which is generated by the Embedded Software ISE9.1i and EDK9.1i,into FPGA chip,and completely meets the needs of the experiment.
This paper discusses in detail the principle of the optical devices in both continuous and discrete variable quantum key distribution,including the classical QKD communication system. A circuit control module using Xilinx Corporation's ML405 Evaluation Platform and suitable for various QKD experiments is proposed. The controller generates necessary nanosecond clock signals for optical devices and integrates quantum cryptography communication system. Finally,the design flow is implemented by downloading the bit stream,which is generated by the Embedded Software ISE9.1i and EDK9.1i,into FPGA chip,and completely meets the needs of the experiment.
Compared with discrete variable quantum key distribution, the Continuous Variable Quantum Key Distribution (CVQKD) system has the advantages of simple equipment, low technical difficulty, and high channel capacity, in addition to unconditional security and detectability for wiretapping. In this paper, the laser light source control system realizes the control and adjustment functions of the photon quantum state, which was encoded with information. In order to generate the synchronous optical pulse signals, the Field Programmable Gate Array (FPGA), multi-channel Digital to Analog Converter (DAC), and micro power Analog to Digital Converter (ADC) were used to control the synchronous optical laser. The control of multiple amplitude modulators and phase modulators is achieved based on the FPGA and high-speed DAC. At present, the electronics performance test of the laser light source control system has been completed, and the results show that the requirements of the CVQKD system index are met.
Based on analysis of working principle and circuit requirement of the phase modulator in quantum key distribution system,the phase modulator drive circuit is designed.The scheme,based on LiNbO3 electro-optic phase modulator,applies FPGA to providing the clock and control signals,while high-precision DAC and high-speed analog switch to producing the drive signal with precision up to nanoseconds.The driver circuit,with low cost,high modulation precision,and low power consumption,could achieve a precise control of optical phase.The experimental result indicates that this design could fully meet the system requirements,and the scheme is of feasibility and reliability.
Abstract The purpose of the FPGA electronic control system for Quantum Key Distribution (QKD) is to improve the analog electronic system in optoelectronic conversion. In the existence of the Mezzanine FPGA board, the main conversion of optical laser signal and optical detector signal can be improved. Mezzanine board can reduce the noise errors during the transmission and receiving a signal. Commonly, the optical signal needs to interface with an analog electronic system. This process requires the conversion process and interfacing with a digital signal to control the optical device and produce a good quality optical signal. The Mezzanine board can reduce the uncertainty during signal conversion and gives the digital capability to control the optical devices. The optical modulation signal for phase modulator control can achieve a full complete phase shift in the Mezzanine board. Plus, the voltage phase has capability up to 10 V with an accuracy of 2.4 µV. The time conversion for phase modulator can be extended in the Mezzanine board based on the digital control signal from FPGA. The system is capable to extend into multiple timing control to handle all the signal and to synchronize the signal in receiving, transmission or in between of the transmission. Thus, the system can handle one way or two-way QKD system accordingly.
Compared with discrete variable quantum key distribution, continuous variable quantum key distribution (CVQKD) has the advantages of low cost, good stability, and high channel capacity, in addition to unconditional security and detectability for wiretapping. The basis of CVQKD system operation is the realization of loading information into photon quantum states. In this paper, a laser light source control system has realized the control and adjustment of the photon quantum states and completed the encoding of quantum states. In order to generate synchronous optical signals, FPGA, multi-channel DAC and micro power ADC are used to control the source of the synchronous optical laser. The control and modulation of multiple optical components are realized based on FPGA, multiple 16-bit 1.0 GSPS DACs and high-performance operational amplifiers. The electronic test results show that the system implements the control and adjustment functions of lasers, amplitude modulator, phase modulators, variable optical attenuators, polarization controllers, as well as detection of synchronized light. The performance of the laser light source control system fully meets the requirements of the CVQKD system.
Phase coding is frequently used in current quantum key distribution(QKD) systems.It has posed many technical challenges on the design of the control electronics.After the description to the overall design of our phase coding QKD system,the paper focuses on the special requirements and implementations on the synchronizing mechanism and automatic phase drift scanning and compensation.The electronics designed in this paper combining with the optical devices can be an independent node device of a QKD network.We have successfully used these node devices to build a practical encrypted communication system through the commercial communication optical fiber system of Wuhu Telecom in Anhui Province.Encrypted communication between multiple nodes by quantum cryptography is implemented in this system.The QKD system in the network actualizes BB84 phase coding protocol at 20MHz repetition rate of light pulses.It achieves quantum bit error rate(QBER)2.95% and secure key generation rate 4.91kbps with a 20km transmission distance.
Quantum Key Distribution (QKD) has garnered significant attention due to its unconditional security based on the fundamental principles of quantum mechanics. While QKD has been demonstrated by various groups and commercial QKD products are available, the development of a fully chip-based QKD system, aimed at reducing costs, size, and power consumption, remains a significant technological challenge. Most researchers focus on the optical aspects, leaving the integration of the electronic components largely unexplored. In this paper, we present the design of a fully integrated electrical control chip for QKD applications. The chip, fabricated using 28 nm CMOS technology, comprises five main modules: an ARM processor for digital signal processing, delay cells for timing synchronization, ADC for sampling analog signals from monitors, OPAMP for signal amplification, and DAC for generating the required voltage for phase or intensity modulators. According to the simulations, the minimum delay is 11ps, the open-loop gain of the operational amplifier is 86.2 dB, the sampling rate of the ADC reaches 50 MHz, and the DAC achieves a high rate of 100 MHz. To the best of our knowledge, this marks the first design and evaluation of a fully integrated driver chip for QKD, holding the potential to significantly enhance QKD system performance. Thus, we believe our work could inspire future investigations toward the development of more efficient and reliable QKD systems.