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arXiv:1906.03763

Quantum random number generation by coherent detection of phase noise

Juan-Rafael Álvarez, Samael Sarmiento, José Antonio Lázaro, Joan M. Gené, Juan P. Torres

Published Jun 6, 2019• 0 citations
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Abstract

We demonstrate a quantum random number generator based on the random nature of the phase difference between two independent laser sources. The speed of random bit generation is determined by the photodetector bandwidth and the linewidth of the lasers used. The system implemented is robust and generates a probability distribution of quantum origin which is intrinsically uniform and thus in principle needs no randomness extraction. The phase is measured with telecom equipment routinely used for high capacity coherent optical communications, which allows to keep track of the phase drift of the lasers and is readily available in the telecommunication industry.

DOI
10.48550/arxiv.1906.03763

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We demonstrate a quantum random number generator based on the random nature of the phase difference between two independent laser sources. The speed of random bit generation is determined by the photodetector bandwidth and the linewidth of the lasers used. The system implemented is robust and generates a probability distribution of quantum origin which is intrinsically uniform and thus in principle needs no randomness extraction. The phase is measured with telecom equipment routinely used for high capacity coherent optical communications, which allows to keep track of the phase drift of the lasers and is readily available in the telecommunication industry.
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The speed of a quantum random number generator is essential for practical applications, such as high-speed quantum key distribution systems. Here, we push the speed of a quantum random number generator to 68 Gbps by operating a laser around its threshold level. To achieve the rate, not only high-speed photodetector and high sampling rate are needed but also a very stable interferometer is required. A practical interferometer with active feedback instead of common temperature control is developed to meet the requirement of stability. Phase fluctuations of the laser are measured by the interferometer with a photodetector and then digitalized to raw random numbers with a rate of 80 Gbps. The min-entropy of the raw data is evaluated by modeling the system and is used to quantify the quantum randomness of the raw data. The bias of the raw data caused by other signals, such as classical and detection noises, can be removed by Toeplitz-matrix hashing randomness extraction. The final random numbers can pass through the standard randomness tests. Our demonstration shows that high-speed quantum random number generators are ready for practical usage.
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