| The most significant advantage of quantum random numbers is its information-theoretic verifiability for random number sequences.The inherent randomness of the quantum world makes it the most attractive method for random number generation.The method of obtaining quantum random numbers by using the fluctuation of the quantum quadrature components of the vacuum state has a practical development prospect.The vacuum state is a pure quantum state,and has the lowest energy.The vacuum state is not directly affected by external physical quantities and is not restricted or related by attackers,so the true random number can be obtained.The quantum noise of the vacuum state is a relatively ideal white Gaussian noise.In principle,different frequencies are independent of each other and have infinite bandwidths and are not correlated with each other.The fluctuations of the detected quantum quadrature components are continuous variables,and a large number of random variables can be obtained during detection.Electronic noise is inevitable in the experiment of generating quantum random numbers.Due to the existence of non-ideal factors such as electronic noise,post-processing is required.In most quantum random number generators,passing the test is the only method used to prove randomness,and if the test fails,the data is algorithmically post-processing until the test passes.In general,the post-processing required to extract entropy is performed offline,so a key direction to improve the post-processing rate is real-time random number post-processing.The real-time yield of the quantum random number needs to reach several Gbps or more.When the analog-to-digital converter samples the original random sequence,the high-efficiency Toeplitz-Hash extraction is a practical solution.Post-processing is limited by FPGA hardware resources and does not make full use of FPGA resources,this leads to higher requirements for FPGA hardware processing resources and performance.Based on FPGA with limited resources,how to realize high-speed real-time safe post-processing of a large number of original random sequences and efficiently utilize FPGA hardware resources has become an unsolved problem in the practical process of quantum random numbers.In this scheme,based on the characteristics of FPGA parallel computing,by monitoring FPGA logic resources and using multiple real-time post-processing to generate multiple independent random bit streams at the same time,the generation rate of quantum random numbers can be greatly improved.We generate a quantum random number scheme based on the measurement of vacuum noise fluctuations.The main tasks are as follows:First,in the experiment,the RF amplifier is used to adjust the voltage signal input to the analog-to-digital converter,so that the analog-to-digital converter with a sampling rate of 240MSa/s and a sampling accuracy of 16 bits can reach the optimal dynamic sampling range;the voltage variance of the original data corresponding to each local oscillator optical power value is recorded,fix the optical power of the local oscillator to obtain the best performance,so as to keep the shot noise higher than the electronic noise spectrum by more than 10d B;four independent high-frequency sideband quantum states were extracted in real-time from the quantum entropy source,and calculated the quantum conditional minimum entropy of each sideband separately.Second,according to the internal structure and calculation characteristics of FPGA,the advantages of FPGA parallel algorithm are invoked,a four-channel post-processing structure is proposed to process the four frequency band modes of the quantum entropy source to improve the performance of post-processing.Theoretical calculation analyzes the total number of multiplication and addition operations required before and after the four-channel post-processing split of the Toeplitz matrix,splitting large Toeplitz matrix within an FPGA.For384×512 Toeplitz matrix,the number of operations is reduced to 49,000 after splitting about1.57 million times.The large-scale Toeplitz matrix is splitted into small ones and multi-cycle distributed processing is performed to ensure hardware stable operation.Thirdly,based on the scheme of generating quantum true random numbers by measuring vacuum noise fluctuations,a real-time hardware post-processing platform is constructed.Real-time and efficient post-processing of quantum random numbers of four channels under the condition of limited computing resources.Based on a single FPGA,the real-time output rate of quantum random numbers up to 10.44Gbps is realized by occupying about 62%of the hardware resources of the FPGA.In this work,the ultra-fast random bit stream output by the quantum random number generator is transmitted to the computer user through the PCIE interface,and the quantum random number correlation coefficient and mutual information of each two channels are maintained at 10-3 and 10-6 respectively.It has passed the NIST test and various other randomness tests,meeting the basic characteristics requirements of true random numbers.It provides technical support and guarantee for the practical application of high-speed confidential communication. |
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