Research On Balanced Homodyne Detector For Quantum Random Number Generation

With the rapid development of communication technology,informatization has become a major trend in current society,and it has profoundly affected all aspects of human production and life.In the process of informatization,a prominent problem,that is,the security of information,is attracting more and more attention.In order to solve this problem,people use random numbers to encrypt information.The quantum entropy source of the quantum random number generator has the nature of uncertainty,which makes the security of the generated quantum random number guaranteed.Based on this advantage,the quantum random number generator gradually enters people's field of vision.However,the generation rate of quantum random numbers is low.Today,when people's requirements for information transmission rate are increasing,this is the biggest shackle of its widespread application.The quantum random number generators based on the orthogonal components of the vacuum state stand out among all kinds of quantum random number generators and have achieved considerable development due to their advantages of easy preparation of quantum states,insensitivity to detection loss,and integration.The balanced homodyne detector can amplify the orthogonal components of the vacuum state to the macro level and can effectively suppress the classical noise.It is an indispensable technical means in the generation of quantum random numbers in the vacuum state.However,with the continuous deepening of research and the increasing requirements for the rate of quantum random number generation,it has been found that the bandwidth of the balanced homodyne detector has become the ultimate limit of the quantum random number generation rate in the vacuum state.Therefore,the research on the balanced homodyne detector become more and more important.This work is dedicated to the research of the balanced homodyne detectors of broadband,high signal-to-noise ratio and good flatness,the balanced homodyne detectors is suitable for the generation of quantum random numbers in the vacuum state.The specific work is carried out as follows.First,we analyzed the working principle and main performance of the balanced homodyne detector.Starting from the key influencing factors of its performance,we established a noise equivalent circuit model to conduct quantitative analysis,determine the selection requirements of components,and complete selection of components.Then,based on the realization and coordination combination of the four functional modules of photocurrent difference signal generation,AC and DC signal separation,AC signal amplification,and DC signal amplification,the circuit schematic diagram of the balanced homodyne detector was designed,and the PCB design and the actual object was made,and an experimental platform was built to test the performance of the balanced homodyne detector such as floor noise,bandwidth,signal-to-noise ratio,common-mode rejection ratio,and DC output response.Faced with the problems in the measured performance,the ADS radio frequency circuit simulation technology was used to simulate and analyze the AC signal amplifier circuit,and the problem was found,and an improvement plan was proposed.After implementing the improvement plan,the improved balanced homodyne detector was simulated and measured,and finally realized a balanced homodyne detector with a floor noise of 5.3m V,a signal-to-noise ratio of 17 d B@0.4m W,a bandwidth of 850 MHz,and a spectrum flatness of±2d B in the frequency range of 300?750MHz.The current experimental results can well meet the basic requirements of vacuum state quantum random number generation for balanced homodyne detectors.This research has laid the foundation for the high-speed generation of quantum random numbers and the integration of quantum random number generators.With the further improvement of the performance of balanced homodyne detectors,quantum random numbers will shine in the field of secure communication.