Quantum nonlocality offers a secure way to produce random numbers: Their unpredictability is intrinsic and can be certified just by observing the statistic of the measurement outcomes, without assumptions on how they are produced. To do this, entangled pairs are generated and measured to violate a Bell inequality with the outcome statistics. However, after a projective quantum measurement, entanglement is entirely destroyed and cannot be used again. This fact poses an upper bound to the amount of randomness that can be produced from each quantum state when projective measurements are employed. Instead, by using weak measurements, some entanglement can be maintained and reutilized, and a sequence of weak measurements can extract an unbounded amount of randomness from a single state as predicted in [Phys. Rev. A 95, 020102(R) (2017)]. We study the feasibility of these weak measurements, analyze the robustness to imperfections in the quantum state they are applied to, and then test them using an optical setup based on polarization-entangled photon pairs. We show that the weak measurements are realizable, but can improve the performance of randomness generation only in close-to-ideal conditions.

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用于认证量子随机性提取的连续弱测量的实验测试

量子非局域性提供了一种产生随机数的安全方法：它们的不可预测性是内在的，并且可以通过观察测量结果的统计数据来证明，而无需假设它们是如何产生的。为此，生成并测量纠缠对以违反带有结果统计数据的贝尔不等式。然而，在投射量子测量之后，纠缠被完全破坏并且不能再次使用。当使用投影测量时，这一事实对每个量子态可以产生的随机性数量提出了上限。相反，通过使用弱测量，可以保持和重新利用一些纠缠，并且一系列弱测量可以从 [ Phys. 牧师 A 95 , 020102(R) (2017)]。我们研究了这些弱测量的可行性，分析了它们所应用的量子态缺陷的鲁棒性，然后使用基于偏振纠缠光子对的光学设置来测试它们。我们表明弱测量是可以实现的，但只能在接近理想的条件下提高随机性生成的性能。