Higher rates for semi-device-independent randomness expansion by recycling input randomness

TL;DR

The paper presents two semi-device-independent quantum randomness expansion protocols that achieve high randomness rates by recycling input randomness or using biased inputs, with proven security and practical feasibility.

Contribution

Introduction of two novel semi-device-independent protocols for randomness expansion, one utilizing recycling of input randomness, both proven secure against quantum side information.

Findings

High randomness rates achievable with as few as 10^5 to 10^6 rounds.

Protocols are secure against quantum side information.

Experimental conditions are realistic for implementation.

Abstract

Although quantum random number generators rely on the inherent indeterminism of quantum mechanics, ensuring that the numbers produced are secure remains a significant challenge. We introduce two semi-device-independent randomness expansion protocols in a prepare-and-measure setting, where the source and measurement devices are treated as uncharacterised and we assume trust only in testing device, which could be implemented using a photodiode. One protocol achieves expansion by recycling the input randomness, while the other uses a biased input distribution to achieve expansion in settings where recycling is not possible. The protocols are proven secure against quantum side information. Our results show that high randomness rates are achievable under experimentally realistic conditions, with expansion obtained in as few as $10^5$ to $10^6$ rounds with the recycling protocol.