标题： 量子信道的量子性 显示英文标题

标题： Quantumness of quantum channels

摘要： 量子相干性是量子物理的一个基本方面，在量子信息科学中起着核心作用。 量子态的这一本质属性在量子操作的影响下可能是脆弱的。 量子相干性被减弱的程度既依赖于信道也依赖于非相干基。 受此启发，我们提出了一种量子信道的非经典性度量方法，即在状态空间的所有正交基集中最小化信道作用后的状态空间的平均量子相干性。 利用量子比特信道的平方$l_1$-范数相干性，可以解析地处理最小化问题，并且所提出的度量具有闭合形式表达式。 如果我们允许信道在一个最大纠缠态上进行局域作用，量子关联会减弱，使状态更加经典。 我们证明了在信道的局域作用下保留量子关联的程度不能超过底层信道的量子特性。 我们进一步将该度量应用于量子隐形传态协议，并表明底层信道的非零量子特性为克服最佳的经典协议提供了一个必要条件。 显示英文摘要

摘要： Quantum coherence is a fundamental aspect of quantum physics and plays a central role in quantum information science. This essential property of the quantum states could be fragile under the influence of the quantum operations. The extent to which quantum coherence is diminished depends both on the channel and the incoherent basis. Motivated by this, we propose a measure of nonclassicality of a quantum channel as the average quantum coherence of the state space after the channel acts on, minimized over all orthonormal basis sets of the state space. Utilizing the squared $l_1$-norm of coherence for the qubit channels, the minimization can be treated analytically and the proposed measure takes a closed form of expression. If we allow the channels to act locally on a maximally entangled state, the quantum correlation is diminished making the states more classical. We show that the extent to which quantum correlation is preserved under local action of the channel cannot exceed the quantumness of the underlying channel. We further apply our measure to the quantum teleportation protocol and show that a nonzero quantumness for the underlying channel provides a necessary condition to overcome the best classical protocols.