Ghosh Subhendu B, Chowdhury Snehasish Roy, Kar Guruprasad, Roy Arup, Guha Tamal, Banik Manik
Physics and Applied Mathematics Unit, <a href="https://ror.org/00q2w1j53">203 B.T. Road Indian Statistical Institute</a>, Kolkata 700108, India.
Department of Physics, A B N Seal College Cooch Behar, West Bengal 736101, India.
Phys Rev Lett. 2024 Jun 21;132(25):250205. doi: 10.1103/PhysRevLett.132.250205.
Quantum nonlocality, pioneered in Bell's seminal work and subsequently verified through a series of experiments, has drawn substantial attention due to its practical applications in various protocols. Evaluating and comparing the extent of nonlocality within distinct quantum correlations holds significant practical relevance. Within the resource theoretic framework this can be achieved by assessing the interconversion rate among different nonlocal correlations under free local operations and shared randomness. In this study we, however, present instances of quantum nonlocal correlations that are incomparable in the strongest sense. Specifically, when starting with an arbitrary many copies of one nonlocal correlation, it becomes impossible to obtain even a single copy of the other correlation, and this incomparability holds in both directions. Such incomparable quantum correlations can be obtained even in the simplest Bell scenario, which involves two parties, each having two dichotomic measurements setups. Notably, there exist an uncountable number of such incomparable correlations. Our result challenges the notion of a "unique gold coin," often referred to as the "maximally resourceful state," within the framework of the resource theory of quantum nonlocality. To this end, we provide examples of isotropic quantum correlations that cannot be distilled up to the Tsirelson point, and thus partially answer a long-standing open question in nonlocality distillation.
量子非定域性由贝尔的开创性工作率先提出,随后通过一系列实验得到验证,因其在各种协议中的实际应用而备受关注。评估和比较不同量子关联中的非定域程度具有重要的实际意义。在资源理论框架内,这可以通过评估在自由局部操作和共享随机性下不同非局域关联之间的相互转换率来实现。然而,在本研究中,我们展示了在最强意义上不可比较的量子非局域关联实例。具体而言,从一个非局域关联的任意多个副本开始,甚至不可能获得另一个关联的单个副本,并且这种不可比较性在两个方向上都成立。即使在最简单的贝尔场景中,即涉及两方且每方都有两个二分测量设置的情况下,也可以获得这种不可比较的量子关联。值得注意的是,存在不可数数量的这种不可比较的关联。我们的结果挑战了量子非定域性资源理论框架内常被称为“最大资源态”的“唯一金币”概念。为此,我们提供了不能蒸馏到齐雷尔森点的各向同性量子关联的例子,从而部分回答了非定域性蒸馏中一个长期存在的开放性问题。