Certified randomness using a trapped-ion quantum processor

Summary

In recent years, numerous theoretical results have shown evidence that quantum computers have the potential to tackle a wide range of problems out of reach of classical techniques. The main examples include factoring large integers6, implicitly solving exponentially sized systems of linear equations7, optimizing intractable problems8, learning certain functions9 and simulating large quantum many-body systems10. However, accounting for considerations such as quantum error correction overheads and gate speeds, the resource requirements of known quantum algorithms for these problems put them far outside the reach of near-term quantum devices, including many suggested fault-tolerant architectures. Consequently, it is unclear whether the devices available in the near term can benefit a practical application11.Starting with one of the first ‘quantum supremacy’ demonstrations5, several groups have used random circuit sampling (RCS) as an example of a task that can be executed faster and with a lower energy cost on present-day quantum computers compared with what is achievable classically4,12,13,14. Yet, despite rapid experimental progress, a beyond-classical demonstration of a practically useful task performed by gate-based quantum computers has so far remained unknown.Random number generation is a natural task for the beyond-classical demonstration because randomness is intrinsic to quantum mechanics, and it is important in many applications, ranging from information security to ensuring the fairness of processes such as jury selection15,16,17. The main challenge for any client receiving randomness from a third-party provider, such as a hardware security module, is to verify that the bits received are truly random and freshly generated. Although certified randomness is not necessary for every use of random numbers, the freshness requirement is especially important in applications such as lotteries and e-games, in which several parties (which may or may not trust each othe...