68 Gbps quantum random number generation by measuring laser phase fluctuations

TL;DR

This paper demonstrates a high-speed quantum random number generator reaching 68 Gbps by measuring laser phase fluctuations with a stable interferometer and advanced digital processing, suitable for practical quantum cryptography.

Contribution

It introduces a practical, high-speed QRNG operating at 68 Gbps using laser phase fluctuation measurement and active feedback stabilization, surpassing previous speeds.

Findings

Achieved 68 Gbps random number generation rate.

Developed a stable interferometer with active feedback.

Generated random numbers passing standard randomness tests.

Abstract

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 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.