Fast real-time random numbers from vacuum fluctuations

Abstract

Summary form only given. The availability of fast and good quality random numbers is necessary to deploy quantum key distribution devices. The state of the universe according to classical mechanics is perfectly determined via its initial conditions. However, in quantum mechanics, the Heisenberg uncertainty relation provides a source of randomness. We present an experiment that taps to this source to provide a fast and reliable stream of random bits.Our experiment setup involves performing a continuous variable homodyne detection of the quantum vacuum state [1]. A 1550 nm fibre coupled laser is split at a 50/50 beam splitter whose outputs are optically coupled to two identical high-speed photo detectors whose photocurrent difference provides a source of entropy. Using methods from classical information theory based on secure hashing functions, the entropy contributions from classical sources, like the electronic dark noise, are characterised and removed from the final generated bits (fig1). This ensures that the randomness in the final bits is solely driven by the quantum fluctuations. The entropy and randomness of the bits generated are being periodically tested using various standard statistical tests on randomness (fig 2). Each test returns a p-value. For a random sequence of numbers, the distributions of the p-values are expected to be uniform.The setup is reliable and robust. To date, it has been continuously generating random bits for more than months at a constant rate of 5.7 Gbits/s. The quantum random numbers are available online [2] via a secure and convenient connection. So far, we have received more than 190000 visits from all over the world served over 40 Gigabytes of random numbers. Each client connection is served with a fresh set of bits.