论文标题
两分态状态的连贯性和两粒子量子相关性的固有程度
Intrinsic degree of coherence of two-qubit states and measures of two-particle quantum correlations
论文作者
论文摘要
最近，已经为经典和单粒子量子状态建立了一种称为内在连贯性的连贯性的基础不变量度[josa b {\ bf 36}，2765（2019）]。使用相同的数学结构，在本文中，我们定义了两量子状态的固有程度，并证明了其在量化两粒子量子相关性和纠缠方面的有用性。在这种情况下，首先，我们表明，两个Quibit状态的固有程度的连贯性使违反贝尔不等式的行为具有上限，并且可以与国家实现，并且具有固有连贯性的两个Qubit状态小于$ 1/\ sqrt {3} $不能抗衡bellate bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell bell。然后，我们表明，两个Quibent状态的量子不一致量化了某些任务中两数Qubit状态中可用的量子相关性的量，这是根据状态的固有程度的上面限制的。接下来，在两粒子纠缠的背景下，我们表明，可以采用的两量子状态同意的值范围取决于两个Qubit状态的内在连贯性以及单个Qubits的固有程度。最后，对于通过泵光子的参数下转换产生的极化两量状态，我们提出了一种实验方案，用于测量两数分状态的固有程度。我们还介绍了我们的理论研究，以表明泵光子的固有固有程度如何决定产生的两量子状态的最大固有程度。
Recently, a basis-invariant measure of coherence known as the intrinsic degree of coherence has been established for classical and single-particle quantum states [JOSA B {\bf 36}, 2765 (2019)]. Using the same mathematical construction, in this article, we define the intrinsic degree of coherence of two-qubit states and demonstrate its usefulness in quantifying two-particle quantum correlations and entanglement. In this context, first of all, we show that the intrinsic degree of coherence of a two-qubit state puts an upper bound on the violations of Bell inequalities that can be achieved with the state and that a two-qubit state with intrinsic degree of coherence less than $1/\sqrt{3}$ cannot violate Bell inequalities. We then show that the quantum discord of a two-qubit state, which quantifies the amount of quantum correlations available in the two-qubit state for certain tasks, is bounded from above by the intrinsic degree of coherence of the state. Next, in the context of two-particle entanglement, we show that the range of values that the concurrence of a two-qubit state can take is decided by the intrinsic degree of coherence of the two-qubit state together with that of the individual qubits. Finally, for the polarization two-qubit states generated by parametric down-conversion of a pump photon, we propose an experimental scheme for measuring the intrinsic degree of coherence of two-qubit states. We also present our theoretical study showing how the intrinsic degree of coherence of a pump photon dictates the maximum intrinsic degree of coherence of the generated two-qubit state.
