Baosheng Zhao

High-speed quantum-random number generation by continuous measurement of arrival time of photons

We demonstrate a novel high speed and multi-bit optical quantum random number generator by continuously measuring arrival time of photons with a common starting point. To obtain the unbiased and post-processing free random bits, the measured photon arrival time is converted into the sum of integral multiple of a fixed period and a phase time. Theoretical and experimental results show that the phase time is an independent and uniform random variable. A random bit extraction method by encoding the phase time is proposed. An experimental setup has been built and the unbiased random bit generation rate could reach 128 Mb/s, with random bit generation efficiency of 8 bits per detected photon. The random numbers passed all tests in the statistical test suite.

Multi-bit quantum random number generation by measuring positions of arrival photons

We report upon the realization of a novel multi-bit optical quantum random number generator by continuously measuring the arrival positions of photon emitted from a LED using MCP-based WSA photon counting imaging detector. A spatial encoding method is proposed to extract multi-bits random number from the position coordinates of each detected photon. The randomness of bits sequence relies on the intrinsic randomness of the quantum physical processes of photonic emission and subsequent photoelectric conversion. A prototype has been built and the random bit generation rate could reach 8 Mbit/s, with random bit generation efficiency of 16 bits per detected photon. FPGA implementation of Huffman coding is proposed to reduce the bias of raw extracted random bits. The random numbers passed all tests for physical random number generator.

The estimation of charge footprint size of ultraviolet photon counting imaging detector with induction readout.

The structure and work principle of an ultraviolet photon counting imaging detector based on wedge and strip anode with induction readout mode are introduced. Two methods of estimating the charge footprint size are presented. One way is theoretical calculation and simulation. The physical course of electrons is simulated from the microchannel plate output side to the readout anode. The calculated results show that the final charge footprint size is sensitive to the thickness of ceramic and not sensitive to the charge footprint size on the Ge layer. The other way is experimental image estimation. The final charge footprint size can be estimated according to the position where the light line of resolution board image begins to bend. Both methods show that the charge footprint size is sensitive to the ceramic substrate. The two methods are simple and effective for estimation of charge footprint size of photon counting imaging detector with induction readout.

Novel space communication technology based on modulated x-ray source

A novel space communication method is presented in this paper based on X-ray photons. As a result of its short wavelength and great penetrability, X-ray has no attenuation for transmission in space when its photon energy is more than 10keV (λ<0.1nm). Thus a communication technology of long distance signal transmission in space can be achieved with smaller volume, lower weight and lower power. Therefore, X-ray communication (XCOM) is especially valuable to the deep space missions, which will be able to realize higher data rates, smaller SWAP than with RF and laser communications. Using X-ray photons as information carrier will not only be a good complement to laser and RF communications, but will also have unique applications when RF and laser signals are not available like the spacecraft’s re-entering to the earth. High-speed modulation and high-sensitivity detection of X-rays are two major technical issues which should be addressed in order for the X-ray communication to take place. A Grid-controlled Modulated X-ray tube (GMXT) is proposed and developed as X-ray transmitter. One or more specially designed grid electrodes are added to the traditional X-ray tube to modulate the electrons. The communication signal is coded and applied to the modulated grid electrode, and then the corresponding X-ray signals are generated and sent out. X-ray detector based on micro-channel plate(MCP) is used as communication receiver because of its high temporal resolution. An audio communication experiment system based on XCOM is setup in laboratory including the X-ray transmitter and the receiver. X-ray communication is successfully demonstrated and the communication speed reaches 64 kilobits per second in a vacuum tube of 6 meters long. As a new concept of space communication, X-ray communication will have more important scientific significance and application prospects when technologies for X-ray modulation and detection are further developed.

X-ray photon-counting detector based on a micro-channel plate for pulsar navigation

The pulse time of arrival (TOA) is a determining parameter for accurate timing and positioning in X-ray pulsar navigation. The pulse TOA can be calculated by comparing the measured arrival time with the predicted arrival time of the X-ray pulse for pulsar. In this study, in order to research the measurement of pulse arrival time, an experimental system is set up. The experimental system comprises a simulator of the X-ray pulsar, an X-ray detector, a time-measurement system, and a data-processing system. An X-ray detector base is proposed on the basis of the micro-channel plate (MCP), which is sensitive to soft X-ray in the 1–10 keV band. The MCP-based detector, the structure and principle of the experimental system, and results of the pulse profile are described in detail. In addition, a discussion of the effects of different X-ray pulse periods and the quantum efficiency of the detector on pulse-profile signal-to-noise ratio (SNR) is presented. Experimental results reveal that the SNR of the measured pulse profile becomes enhanced as the quantum efficiency of the detector increases. The SNR of the pulse profile is higher when the period of the pulse is smaller at the same integral.

The resolution estimation of wedge and strip anodes

A new resolution estimation method for wedge and strip anode based on the single photon imaging configuration is provided. The limiting resolution estimation equation is deduced theoretically according to the threshold principle. The relation between the charge cloud and the covered electrodes is discussed, and the equivalent diameter number is calculated. The resolution equation for the position deviation amplitude or FWHM is provided if noise exists. The relation between the position deviation amplitude and the total charge deviation amplitudes is discussed. The constancy of the position deviation amplitudes versus positions is provided. The results calculated from these equations are discussed. According to the equations, it is indicated that the spatial resolution is affected by the detection system configuration and noise. These conclusions may be useful for the designing and performance improvement of future photon imagers.

Ghosting phenomena in single photon counting imagers with Vernier anode

We provide the ghosting theory of two-dimensional Vernier anode based imagers. The single photon counting detection system based on Vernier anode is constructed. The ghosting, which occurs during the decoding of two-dimensional Vernier anode, and its possible solutions are described in detail. On the basis of the discussion of the decoding algorithm, the ghosting theoretical model is established. Phase conditions on which imaging ghosting can be avoided and the probability distribution function are proposed; the root causes of ghosting of two-dimensional Vernier anode are also discussed.

Correction of ultraviolet single photon counting image distortion

Single photon counting imaging technology has been widely used in space environment detection, astronomy observation, nuclear physics, and ultraweak bioluminescence. However, the distortion of the single photon counting image will badly affect the measurement results. Therefore, the correction of distortion for single photon counting image is very significant. Ultraviolet single photon imaging system with wedge and strip anode is introduced and the influence factor leading to image distortion is analyzed. To correct original distorted image, three different image correction methods, namely, the physical correction, the global correction, and the local correction, are applied. In addition, two parameters, i.e., the position index and the linearity index, are defined to evaluate the performance of the three methods. The results suggest that the correction methods can improve the quality of the initial image without losing gray information of each counting light spot. And the local correction can provide the best visual inspections and performance evaluation among the three methods.

Selection of MCP for array X-ray pulsar navigation detector

According to the demands of an array detector in the X-ray pulsar navigation system for Micro-channel Plate (MCP), a selection method for the MCP was explored. Four key parameters for the selection of MCPs, the uniformity of gain, impedance matching, dark count rate and the gain coefficient were determined. Based on the four key parameters, corresponding experiments were designed and the selection process of MCPs was set out. The amplitudes and counting rates of MCPs selected by proposed method were tested. The tested results show that the relative error of each detection unit is not identical. When a single channel anode is used, the ranges of the maximum relative error Δ1i and minimum relative error Δ2i of the amplitudes for output signals from the ith anode are 7%-13.5% and 3%-6.7%, respectively, and when a four-channel anode is used, Δ1i and Δ2i are 7.8% and 3.1%, respectively. Moreover, the relative error between the anode count rate n1+n2+n3+n4 from the single channel and N from the four-channel shared anode is 4.38%, less than 10%. Obtained results indicate that the MCPs with good performance have been effectively chosen by the proposed selection method. ©, 2015, Chinese Academy of Sciences. All right reserved.

Continuous measurement of the arrival times of x-ray photon sequence

In order to record x-ray pulse profile for x-ray pulsar-based navigation and timing, this paper presents a continuous, high-precision method for measuring arrival times of photon sequence with a common starting point. In this method, a high stability atomic clock is counted to measure the coarse time of arrival photon. A high resolution time-to-digital converter is used to measure the fine time of arrival photon. The coarse times and the fine times are recorded continuously and then transferred to computer memory by way of memory switch. The pulse profile is obtained by a special data processing method. A special circuit was developed and a low-level x-ray pulse profile measurement experiment system was setup. The arrival times of x-ray photon sequence can be consecutively recorded with a time resolution of 500 ps and the profile of x-ray pulse was constructed. The data also can be used for analysis by many other methods, such as statistical distribution of photon events per time interval, statistical distribution of time interval between two photon events, photon counting histogram, autocorrelation and higher order autocorrelation.