Dong-xu Yang

A Bias-Free Quantum Random Number Generation Using Photon Arrival Time Selectively

We present a high-quality quantum random number generator (QRNG) without posting processing using photon arrival time selectively in accordance with the number of photon detection events within a sampling time interval in attenuated light. It is well showed in both theoretical analysis and experiments verification that this random number production method eliminates both bias and correlation perfectly without post processing and the random number can be clearly passed the standard randomness tests. We fulfill theoretical analyses and experimental verification of the method whose rate can reach up to 45Mbps.We present a high-quality bias-free quantum random number generator (QRNG) using photon arrival time selectively, in accordance with the number of photon detection events within a sampling time interval in attenuated light. It is well shown in both theoretical analysis and experimental verification that this random number production method eliminates both bias and correlation perfectly without more postprocessing and that the random number can clearly pass the standard randomness tests. We fulfill theoretical analysis and experimental verification of the method whose rate can reach up to 45 Mb/s.

Field Test of Measurement-Device-Independent Quantum Key Distribution

The main type of obstacles of practical applications of quantum key distribution (QKD) network are various attacks on detection. Measurement-device-independent QKD (MDIQKD) protocol is immune to all these attacks, and thus, a strong candidate for network security. Recently, several proof-of-principle demonstrations of MDIQKD have been performed. Although novel, those experiments are implemented in the laboratory with secure key rates less than 0.1 b/s. Besides, they need manual calibration frequently to maintain the system performance. These aspects render these demonstrations far from practicability. Thus, justification is extremely crucial for practical deployment into the field environment. Here, by developing an automatic feedback MDIQKD system operated at a high clock rate, we perform a field test via deployed fiber network of 30 km total length achieving a 16.9 b/s secure key rate. The result lays the foundation for a global quantum network, which can shield from all the detection-side attacks.

Design of Ultra-Low Noise and Low Temperature Usable Power System for High-Precision Detectors

In high-precision detector systems, the power supply usually need to be ultra-low noise and stabilized. Design and implementation of an ultra-low noise power supply is described in this paper. We implemented and tested the power system actually in a scientific CCD (Charge-coupled device) detector system, but the design structure could be used in many high-precision detector systems as infrared detector or high-energy particles detectors. The power system uses DC-DC switching regulators and LDO regulators for power generating, uses multi-stage filters for noise reducing. Multi-output power supply with noise about 40 μVrms is achieved, the overall energy efficiency is 68.5%. Besides, the electronic system takes the low temperature as an important consideration, and the system has been tested in an extreme environment as low as 193 K.

Design of ultra-low noise power system for high-precision detectors

In this paper, we introduce an ultra-low noise power system designed for high precision detectors, like CCD detector. We build low noise power circuit for the front-end electronics, whose noise generally needs to be under 1 mVrms. Because the system may be used in low temperature environment as in Antarctica, the influence of electronic equipment working at 213K-193K is fully considered in the beginning of the design. As a result, the power system passed noise and long-time low temperature test.

An energy measurement method of high-frequency narrow laser pulse based on FPGA

An energy measurement method used for high-frequency narrow laser pulses based on a high performance field-programmable gate array (FPGA) chip is introduced in this paper. There are two parts contained in this method: signal conditioning and data processing. The signal conditioning part will transform the incident narrow laser pulse to electrical signal which has an appropriate width and the amplitude is linear to the energy of the laser pulse. The electrical signal will be digitalized by a high speed ADC and input to the FPGA chip in the data processing part. The amplitude of the electrical signal will be obtained by real-time calculations in the FPGA. The test result shows that the method is suitable for the laser pulse with FWHW low level with 200ps and frequency up to 20MHz.

Real-time energy measurement of high repetition rate ultrashort laser pulses using pulse integration and FPGA processing

Real-time energy measurement using pulse integration method for high repetition rate ultrashort laser pulses based on FPGA (Field-Programmable Gate Array) and high-speed pipeline ADC (Analog-to-Digital Convertor) is introduced in this paper. There are two parts contained in this method: pulse integration and real-time data processing. The pulse integration circuit will convert the pulse to the step type signals which are linear to the laser pulse energy. Through the real-time data processing part, the amplitude of the step signals will be obtained by ADC sampling and conducting calculation in real time in FPGA. The test result shows that the method with good linearity (4.770%) and without pulse measurement missing is suitable for ultrashort laser pulses with high repetition rate up to 100 MHz.

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.

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.