Real-Time 50-Gbit/s Spatially Multiplexed Quantum Random Number Generator Based on Vacuum Fluctuation

Unpredictable random number (RN) generation is an essential technology for cryptographic applications. Quantum RN generators (QRNGs) have attracted significant attention owing to their generation of RNs utilizing the randomness guaranteed by quantum mechanics. Vacuum fluctuations are a promising entropy source for QRNGs. The quantum true randomness is detected using a homodyne setup with a laser source and a beam splitter. QRNGs based on vacuum fluctuations can generate RNs at a high-speed and in a stable manner. This article reports a high-speed spatially multiplexed QRNG based on vacuum fluctuations using a single semiconductor laser diode and an integrated optical beam splitter. The QRNG obtained four independent vacuum fluctuations across a wide bandwidth of over 2 GHz. The RNs were extracted in parallel using a field-programmable gate array with analog-to-digital converters. An aggregated real-time RN generation rate of 4×12.5 Gbit/s was achieved. The generated RNs passed a randomness test based on NIST SP800-90B.