Gómez S, Uzcátegui D, Machuca I, Gómez E S, Walborn S P, Lima G, Goyeneche D
Departamento de Física, Universidad de Concepción, 160-C, Concepción, Chile.
ANID-Millennium Science Initiative Program-Millennium Institute for Research in Optics, Universidad de Concepción, 160-C, Concepción, Chile.
Sci Rep. 2021 Oct 14;11(1):20489. doi: 10.1038/s41598-021-99844-2.
Certification of quantum nonlocality plays a central role in practical applications like device-independent quantum cryptography and random number generation protocols. These applications entail the challenging problem of certifying quantum nonlocality, something that is hard to achieve when the target quantum state is only weakly entangled, or when the source of errors is high, e.g. when photons propagate through the atmosphere or a long optical fiber. Here we introduce a technique to find a Bell inequality with the largest possible gap between the quantum prediction and the classical local hidden variable limit for a given set of measurement frequencies. Our method represents an efficient strategy to certify quantum nonlocal correlations from experimental data without requiring extra measurements, in the sense that there is no Bell inequality with a larger gap than the one provided. Furthermore, we also reduce the photodetector efficiency required to close the detection loophole. We illustrate our technique by improving the detection of quantum nonlocality from experimental data obtained with weakly entangled photons.
量子非定域性的认证在诸如设备无关量子密码学和随机数生成协议等实际应用中起着核心作用。这些应用带来了认证量子非定域性这一具有挑战性的问题，当目标量子态仅为弱纠缠态，或者误差源很大时，例如光子在大气或长光纤中传播时，这很难实现。在此，我们引入一种技术，用于针对给定的一组测量频率，找到量子预测与经典局域隐变量极限之间具有最大可能差距的贝尔不等式。我们的方法代表了一种从实验数据认证量子非局域关联的有效策略，无需额外测量，从这个意义上说，不存在比所提供的差距更大的贝尔不等式。此外，我们还降低了闭合探测漏洞所需的光电探测器效率。我们通过改进对用弱纠缠光子获得的实验数据的量子非定域性探测来说明我们的技术。
