Enhancing entropy in quantum random number generator

Unique true random numbers with information-theoretically provable randomness can be generated based on homodyne detection of quantum vacuum state and universal-hashing randomness extraction. To increase the min-entropy in the raw data and enhance the generation rate of true random number, the influence of classical noise excursion, which may be intrinsic to a system or deliberately induced by an eavesdropper, on the min-entropy of the raw data is discussed in the optimum dynamical ADC range scenario. We propose enhancing local oscillator intensity rather than electrical gain for noise-independent amplification of quadrature fluctuation of vacuum state. Abundant min-entropy is extractable from the raw data even when classical noise excursion is large. The quality and generation speed of the quantum random number generator are guaranteed. Experimentally, when classical noise excursions of the raw data is about 17.2 times of the classical noise standard deviation. An extraction ratio of true randomness of 85.3% is achieved by finite enhancement of the local oscillator power.