The Development Of Several Key Instrument In Quantum Security Communication

Quantum mechanics is one of the greatest discovery of physics in the last century, it reveals many microscopic phenomena violating human visual.Quantum mechanics develop human beings'perspective, expand human beings'cognition, and has created a whole new area of research. Quantum information science is a new discipline that used of the quantum mechanical properties of micro-particles, and combinate with the traditional information science. In quantum information, quantum secure communication can be achieved absolute security, and has more advantages compared thd classic communication. Also It has very high practical value. Quantum cryptography network based on fiber-optic is the only implementation of quantum information in the field of practical currently. These features make quantum secure communication become a hot area of communication. The major research institutions at home and abroad have put a lot of human resources and research funds to the development of quantum secure communication technology. So it is developed very rapid.The equipment of quantum secure communication is composed of electronics devices and optical devices. The main content of this article is the development of three key electronics devices, the laser sources, synchronous system and the single photon detector, that based on optical-fiber quantum secure communication. Two optical quantum cryptography experiments are introduced also.First of all, in the first chapter of this paper, the basic knowledge of quantum mechanics and quantum information are introduced briefly. The history and current development of quantum secure communication are also introduced. The decisive influence of the three key electronics devices on the whole quantum secure communication is pointed out.In the second chapter, the theories and techniques of the optical-fiber quantum secure communication are descripted detailly. The theory of quantum mechanics which guaranteeing absolute security of communication, various coding schemes, the mode of quantum states, security vulnerabilities there and prevention patterns are discussed in detail.The third chapter is the work of development of single-photon source. Three types of lasers that developed independently by us are introduced.The one is a narrow pulse laser that working in the quantum phone system, as the signal single-photon source and synchronous laser source of the telephone; the second is the high-speed pulses laser that working in the remote quantum key distribution system,in to meet the requirements of high-frequency and long distance; the last is a ultra-short pulse laser for the test platform system of the high-speed single photon detectors, specially designed to accommodate the ultra-narrow door width of the high-speed single-photon detectors.To protect the fiber-optic quantum cryptography system up into a high rate and low error rate, both sides of the communications must have a synchronous system achieved minimum time shaking. The fourth chapter is the working of development of the synchronous systems by us. Synchronization laser and signal laser are transmited along the same optical fiber in use of the WDM technic,so that synchronization laser and signal laser relative to the minimum shaking.Then the photoelectric converter and the discriminator which has high time resolution are used to discriminate the synchronization laser. Synchronous system meets the requirement of time shaking of the system finally.The frequency of infrared single-photon detector has become a bottleneck of code rate and communication range increasing in quantum cryptography communication in fiber. In order to solve this problem, we initiated the work of developing high-speed infrared Semiconductor Single Photon detector. In the high-speed single-photon detector, weak avalanche signal extraction is the difficult, in this article, the band stop filter and the self-differecing circuit had been used to extract the weak avalanche signal.A setup of test platform for the high-speed single-photon detector was built also.The performance of the detector's had been measured completely.At the last of this article, two fiber quantum cryptography experiments were introduced, in order to validate the performance of the electronics devices in other ways. The first experiment is the world's first quantum-phone based on quantum secure communication in fiber.The narrow-pulse single-photon source and synchronization system played a key role in this study that the quantum key rate has meet the requirements of real-time call. Another experiment is the long-distance quantum key distribution in fiber which has the longest secure distance in the world.The high-speed laser has been working as a single photon source in this experiment.The quantum key had been generated successfully over a distance of 200km.The main innovations of this paper are:(1) Using narrow pulse forming circuit to modulate the semiconductor laser that makes the laser pulse width less than 1ns.Useing precise temperature control to stabilize the wavelength, line-width and power of the laser. Using high-performance FPGA and serial-parallel conversion technology to achieve the electronics frequency of 1GHz and laser pulse frequency of 500MHz.Using high-speed avalanche to narrow the pulse width of the laser less than 100ps.(2) Using laser and the photoelectric conversion technique to extract the signal, and using the consistent speed of signal lignt and synchronous light to develop the synchronization system. Using WDM technology to couple the signal light and synchronous light into the same fiber that make sure the same time of their transmition.(3)Using the mode of a weak avalanche to control the dark count level and after-pulse probability of the infrared single-photon detector, so that to work in high-speed conditions. The avalanche diode differential response signal was inhibite through the self-designed filter and the self-differecing circuit. And also the weak avalanche signal was extracted successfully. Building a test platform for the high-speed single-photon detector that can test almost whole performance of the detector.