Centre for Quantum Computation and Communication Technology, Research School of Engineering, The Australian National University, Canberra, ACT, 2601, Australia.
Centre for Quantum Computation and Communication Technology, Department of Quantum Science, The Australian National University, Canberra, ACT, 2601, Australia.
Sci Rep. 2023 Jan 25;13(1):1436. doi: 10.1038/s41598-023-28035-y.
Quantum correlation often refers to correlations exhibited by two or more local subsystems under a suitable measurement. These correlations are beyond the framework of classical statistics and the associated classical probability distribution. Quantum entanglement is the most well-known of such correlations and plays an important role in quantum information theory. However, there exist non-entangled states that still possess quantum correlations which cannot be described by classical statistics. One such measure that captures these non-classical correlations is discord. Here we introduce a new measure of quantum correlations which we call entropic accord that fits between entanglement and discord. It is defined as the optimised minimax mutual information of the outcome of the projective measurements between two parties. We show a strict hierarchy exists between entanglement, entropic accord and discord for two-qubit states. We study two-qubit states which shows the relationship between the three entropic quantities. In addition to revealing a class of correlations that are distinct from discord and entanglement, the entropic accord measure can be inherently more intuitive in certain contexts.
量子关联通常是指在适当测量下两个或多个局部子系统表现出的相关性。这些相关性超出了经典统计学和相关经典概率分布的范围。量子纠缠是最著名的此类相关性，在量子信息理论中起着重要作用。然而，存在非纠缠态，它们仍然具有无法用经典统计学描述的量子相关性。一种可以捕捉这些非经典相关性的度量是失协。在这里，我们引入了一种新的量子相关性度量，我们称之为熵协调，它介于纠缠和失协之间。它被定义为两个当事方之间的投影测量结果的最优极大极小互信息。我们表明，对于两量子比特态，存在着严格的等级制度，即纠缠、熵协调和失协之间的等级制度。我们研究了两量子比特态，揭示了这三种熵量之间的关系。除了揭示与失协和纠缠不同的一类相关性外，熵协调度量在某些情况下可以更直观。
