Practical randomness and privacy amplification

We present the first complete implementation of a randomness and privacy amplification protocol based on Bell tests. This allows the building of device-independent random number generators which output provably unbiased and private numbers, even if using an uncharacterised quantum device potentially built by an adversary. Our generation rates are linear in the runtime of the quantum device and the classical randomness post-processing has quasi-linear complexity – making it efficient
on a standard personal laptop. The statistical analysis is tailored for real-world quantum devices, making it usable as a quantum technology today.

We then showcase our protocol on the quantum computers from the IBM-Q experience. Although not purposely built for the task, we show that quantum computer can run faithful Bell tests by adding minimal assumptions. At a high level, these amount to trusting that the quantum device was not purposely built to trick the user, but otherwise remains mostly uncharacterised. In this semi-device-independent manner, our protocol generates provably private and unbiased random
numbers on today’s quantum computers.

Cameron Foreman, Sherilyn Wright, Alec Edgington, Mario Berta, Florian J. Curchod

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