Abstract

Quantum non-locality not only challenges our intuitions about nature, it has been put to work in the nascent field of device-independent quantum information. In particular, certification of true randomness can be achieved by non-local correlations if one accepts the validity of the no-signalling principle. A large repertoire of protocols has emerged for randomness certification, expansion and amplification. These protocols tend to be rather costly in terms of ebits. It is natural to ask whether one can do better with less and we show that this is indeed possible: more bits of randomness from the same ebit. This is achieved via making sequences of measurements thus expanding the traditional Bell test scenario. This in itself offers up interesting and novel possibilities for device-independent randomness certification.