Ma Zhonghua, Rambach Markus, Goswami Kaumudibikash, Bhattacharya Some Sankar, Banik Manik, Romero Jacquiline
Australian Research Council Centre of Excellence for Engineered Quantum Systems and School of Mathematics and Physics, University of Queensland, Queensland 4072, Australia.
Department of Computer Science, QICI Quantum Information and Computation Initiative, The University of Hong Kong, Pokfulam Road, Hong Kong.
Phys Rev Lett. 2023 Sep 29;131(13):130201. doi: 10.1103/PhysRevLett.131.130201.
Quantum correlations and nonprojective measurements underlie a plethora of information-theoretic tasks, otherwise impossible in the classical world. Existing schemes to certify such nonclassical resources in a device-independent manner require seed randomness-which is often costly and vulnerable to loopholes-for choosing the local measurements performed on different parts of a multipartite quantum system. In this Letter, we propose and experimentally implement a semi-device-independent certification technique for both quantum correlations and nonprojective measurements without seed randomness. Our test is semi-device independent in the sense that it requires only prior knowledge of the dimension of the parts. We experimentally show a novel quantum advantage in correlated coin tossing by producing specific correlated coins from pairs of photons entangled in their transverse spatial modes. We establish the advantage by showing that the correlated coin obtained from the entangled photons cannot be obtained from two two-level classical correlated coins. The quantum advantage requires performing qubit trine positive operator-valued measures (POVMs) on each part of the entangled pair, thus also certifying such POVMs in a semi-device-independent manner. This proof of concept firmly establishes a new cost-effective certification technique for both generating nonclassical shared randomness and implementing nonclassical measurements, which will be important for future multiparty quantum communications.
量子关联和非投影测量是众多信息理论任务的基础，否则在经典世界中是不可能实现的。以设备无关的方式认证此类非经典资源的现有方案需要种子随机性——这通常成本高昂且容易出现漏洞——用于选择在多体量子系统的不同部分上执行的局部测量。在本信函中，我们提出并通过实验实现了一种用于量子关联和非投影测量的半设备无关认证技术，且无需种子随机性。我们的测试在某种意义上是半设备无关的，即它仅需要各部分维度的先验知识。我们通过从在其横向空间模式中纠缠的光子对产生特定的关联硬币，在关联抛硬币实验中通过实验展示了一种新颖的量子优势。我们通过表明从纠缠光子获得的关联硬币无法从两个两能级经典关联硬币获得来确立这种优势。这种量子优势需要在纠缠对的每个部分上执行量子比特三态正算子值测量（POVM），因此也以半设备无关的方式认证了此类POVM。这一概念验证牢固地确立了一种用于生成非经典共享随机性和实现非经典测量的新的具有成本效益的认证技术，这对于未来的多方量子通信将是重要的。
