Baccari F, Augusiak R, Šupić I, Tura J, Acín A
ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain.
Center for Theoretical Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warsaw, Poland.
Phys Rev Lett. 2020 Jan 17;124(2):020402. doi: 10.1103/PhysRevLett.124.020402.
Bell inequalities constitute a key tool in quantum information theory: they not only allow one to reveal nonlocality in composite quantum systems, but, more importantly, they can be used to certify relevant properties thereof. We provide a general construction of Bell inequalities that are maximally violated by the multiqubit graph states and can be used for their robust self-testing. Apart from their theoretical relevance, our inequalities offer two main advantages from an experimental viewpoint: (i) they present a significant reduction of the experimental effort needed to violate them, as the number of correlations they contain scales only linearly with the number of observers; (ii) numerical results indicate that the self-testing statements for graph states derived from our inequalities tolerate noise levels that are met by present experimental data. We also discuss possible generalizations of our approach to entangled states whose stabilizers are not tensor products of Pauli matrices. Our work introduces a promising approach for the certification of complex many-body quantum states.
它们不仅能让人揭示复合量子系统中的非定域性，更重要的是，可用于验证其相关特性。我们给出了一种贝尔不等式的通用构造，这种不等式会被多量子比特图态最大程度地违背，并且可用于其稳健的自测试。除了理论相关性外，从实验角度来看，我们的不等式有两个主要优点：（i）违反这些不等式所需的实验工作量显著减少，因为它们包含的相关性数量仅与观测者数量呈线性关系；（ii）数值结果表明，从我们的不等式推导得出的图态自测试陈述能够容忍当前实验数据所达到的噪声水平。我们还讨论了将我们的方法推广到稳定子不是泡利矩阵张量积的纠缠态的可能性。我们的工作为复杂多体量子态的验证引入了一种很有前景的方法。
