Previous realizations of quantum random number generators (QRNGs) have relied on phenomena ranging from the vacuum-state fluctuations of the electromagnetic field to phase noise measurements. Now, Yicheng Shi and collaborators have combined a QRNG based on vacuum fluctuations with a fast randomness extractor to produce uniformly distributed random bits at a rate around 480 Mbit s−1. The vacuum fluctuations were measured with a balanced homodyne detector where the vacuum field was mixed with a field generated by a local oscillator (a continuous-wave laser); two photodiodes detected the optical output signals and performed current subtraction. The total noise associated with this photocurrent difference was then fed into an analog-to-digital converter to obtain 16-bit samples. To generate random numbers that are unpredictable as well as uniformly distributed, the digital output was further processed with a randomness extractor based on a linear feedback shift register.
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Donati, G. Randomness from vacuum. Nature Photon 10, 565 (2016). https://doi.org/10.1038/nphoton.2016.167
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DOI: https://doi.org/10.1038/nphoton.2016.167
