Ke Cui

Experimental unconditionally secure bit commitment

Quantum physics allows for unconditionally secure communication between parties that trust each other. However, when the parties do not trust each other such as in the bit commitment scenario, quantum physics is not enough to guarantee security unless extra assumptions are made. Unconditionally secure bit commitment only becomes feasible when quantum physics is combined with relativistic causality constraints. Here we experimentally implement a quantum bit commitment protocol with relativistic constraints that offers unconditional security. The commitment is made through quantum measurements in two quantum key distribution systems in which the results are transmitted via free-space optical communication to two agents separated with more than 20 km. The security of the protocol relies on the properties of quantum information and relativity theory. In each run of the experiment, a bit is successfully committed with less than 5.68×10(-2) cheating probability. This demonstrates the experimental feasibility of quantum communication with relativistic constraints.

High-speed arbitrary waveform generator based on FPGA

With the development of electronic and information technology, the signal generator has been widely used in various fields of electronic technology. And the requirement of its performance is increasingly more and more superior, such as adjustable frequency and range, high frequency stability, fast conversion speed, etc. Meanwhile, Some uncommonly special waveforms are needed in some special environment, for example a waveform of 1/(T-t) form used in quantum random number generator. Therefore high-speed and stability arbitrary waveform generator have great significance for the practical application of scientific research. In this paper, the design of the arbitrary waveform generator is based on a FPGA chip: XC6SLX75T, using the DDS technology and a high-speed DAC, the digital sampling frequency is up to 1GHz.

A Real-Time Design Based on FPGA for Expeditious Error Reconciliation in QKD System

For high-speed quantum key distribution systems, error reconciliation is often the bottleneck affecting system performance. By exchanging common information through a public channel, the identical key can be generated on both communicating sides. However, the necessity to eliminate disclosed bits for security reasons lowers the final key rate. To improve this key rate, the amount of disclosed bits should be minimized. In addition, decreasing the time spent on error reconciliation also improves the key rate. In this paper, we introduce a practical method for expeditious error reconciliation implemented in a field programmable gate array for a discrete variable quantum key distribution system, and illustrate the superiority of this method to other similar algorithms running on a PC. Experimental results demonstrate the rapidity of the proposed protocol.

Design of a high-repetition rate photon source in a quantum key distribution system

Photon source with high-repetition quantum message transmission is needed in the quantum key distribution (QKD) system for long distance and high-repetition rate. We design high-repetition-rate weak coherent light by applying a practical QKD system with decoy states and polarization coding including an FPGA-based true random number generator, narrow pulse shaping under the modulation of high-speed true random number as well as its laser driver. The test indicates that the repetition rate of such light can attain a high performance of 650 MHz, pulse width less than 300 ps, stability of pulse amplitude better than 5%, and extinction rate better than 1000:1.

A Generic Reconfigurable System With High-Speed Data Transmission and High-Precision Time Measurements Applied to a Quantum Bit Commitment Experiment

A reconfigurable system with high-speed data transmission and high-precision time measurement capability based on optical fiber and FPGA technology is presented in this paper. The design is generic for applications where data transmission and time measurement are required. This could be adapted to particle physic experiment, large imaging system, quantum bit commitment, etc. The system is extendable and reconfigurable, allowing data transmission in a bandwidth of 7.5 Gbps. TDC-GPX for time measurement, signal conditioning, data storage, real-time data processing with an FPGA with standard interface such as USB 2.0 and an expansion interface are included. As an example of an application, the design for bit commitment experiment is fully introduced.

Generic design of master board of CCD controller

In this paper, the master board of CCD controller is designed for scientific CCD imaging system. The master controller board with FPGA control center, provides all of the timing clock to the clock and bias board and the data acquisition board which connect to the CPCI backplane, and USB3.0 high-speed serial bus and fiber optic interface.

A data transmission and time measurement system for bit commitment experiment

A data transmission and time measurement system for bit commitment experiment is introduced in this paper. The design is for requirement of fast data transmission and time measurement of bit commitment experiment including high bandwidth data transmission, storage, real time processing with FPGA, USB 2.0, FPGA-based TDC and TDC-GPX for time measurement. The system is applied in the bit commitment experiments successfully.

Experimental Realization of Measurement Device Independent Quantum Key Distribution

We report a complete experimental realization of measurement device independent quantum key distribution system with decoy method, which closes loopholes in both source and detection. 25-kbit secure key is generated over a 50-km fiber link.