Device-independent randomness expansion against quantum side information

TL;DR

This paper reports the first experimental demonstration of device-independent randomness expansion using a Bell test with high-efficiency single-photon detectors, achieving a significant net gain of certified random bits and establishing security against quantum adversaries.

Contribution

It introduces a practical setup for device-independent randomness expansion with tight security bounds, advancing towards commercial viability.

Findings

Achieved a net gain of 2.57×10^8 certified bits.

Used a Bell test with 84% detection efficiency and a spot-checking protocol.

Generated randomness at a rate of 13,527 bits per second.

Abstract

The ability to produce random numbers that are unknown to any outside party is crucial for many applications. Device-independent randomness generation does not require trusted devices and therefore provides strong guarantees of the security of the output, but it comes at the price of requiring the violation of a Bell inequality for implementation. A further challenge is to make the bounds in the security proofs tight enough to allow randomness expansion with contemporary technology. Although randomness has been generated in recent experiments, the amount of randomness consumed in doing so has been too high to certify expansion based on existing theory. Here we present an experiment that demonstrates device-independent randomness expansion. By developing a Bell test setup with a single-photon detection efficiency of around $84\%$ and by using a spot-checking protocol, we achieve a net gain of $2.57\times10^8$ certified bits with a soundness error $3.09\times10^{-12}$. The experiment ran for $19.2$ h, which corresponds to an average rate of randomness generation of $13,527$ bits per second. By developing the entropy accumulation theorem, we establish security against quantum adversaries. We anticipate that this work will lead to further improvements that push device-independence towards commercial viability.