We propose the first correct special-purpose quantum circuits for preparation of Bell-diagonal states (BDS), and implement them on the IBM Quantum computer, characterizing and testing complex aspects of their quantum correlations in the full parameter space. Among the circuits proposed, one involves only two quantum bits but requires adapted quantum tomography routines handling classical bits in parallel. The entire class of Bell-diagonal states is generated, and a number of characteristic indicators, namely entanglement of formation, CHSH non-locality, steering and discord, are experimentally evaluated over the full parameter space and compared with theory. As a by-product of this work we also find a remarkable general inequality between "quantum discord" and "asymmetric relative entropy of discord": the former never exceeds the latter. We also prove that for all BDS the two coincide.

中文翻译：

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贝尔对角线和维尔纳状态生成：IBM 量子计算机上的纠缠、非局域性、转向和不和谐

我们提出了第一个正确的专用量子电路，用于准备贝尔对角线态 (BDS)，并在 IBM 量子计算机上实现它们，在全参数空间中表征和测试其量子相关性的复杂方面。在提出的电路中，一个只涉及两个量子位，但需要经过调整的量子断层扫描程序并行处理经典位。生成了整类贝尔对角线状态，并在整个参数空间上通过实验评估了许多特征指标，即编队纠缠、CHSH 非局域性、转向和不和谐，并与理论进行了比较。作为这项工作的副产品，我们还发现“量子不和谐”和“不和谐的不对称相对熵”之间存在显着的普遍不等式：前者永远不会超过后者。我们还证明，对于所有 BDS，两者是一致的。