利用测量诱导扰动的退相干量子行走中的量子度
Quantumness in decoherent quantum walk using measurement-induced disturbance
摘要：
线或n圈上的退相干离散时间量子行走的经典化可以用各种方式来证明，这些方式不一定提供几何无关的描述。例如，在前一种情况下，位置概率分布变得越来越高斯，伴随着标准偏差的下降，但在后一种情况下不是这样。作为另一示例，线上的量子行走的每个步骤可以经受任意相位门，而不影响位置概率分布，无论行走是无噪声的还是有噪声的。这种对称性，这是缺乏的情况下，无噪声循环行走，但恢复存在足够的噪音，作为一个指标的经典化，但只有在循环的情况下。在这里，我们表明，硬币和位置自由度之间的量子相关程度，通过基于由局部测量引起的干扰的测量来量化（Luo，Phys.Rev.A77，022301（2008）），提供了跨越两种类型的步行的经典化的合适测量。应用这一措施来比较这两种行走，我们发现，循环量子行走往往经典化速度比量子行走线，因为更有效的相位随机化由于两个反向旋转波的自干涉。我们将噪声建模为作用在硬币上，并由压缩广义振幅阻尼（SGAD）通道给出，该通道推广了广义振幅阻尼通道。
英文摘要：
The classicalization of a decoherent discrete-time quantum walk on a line or an n-cycle can be demonstrated in various ways that do not necessarily provide a geometry-independent description. For example, the position probability distribution becomes increasingly Gaussian, with a concomitant fall in the standard deviation, in the former case, but not in the latter. As another example, each step of the quantum walk on a line may be subjected to an arbitrary phase gate, without affecting the position probability distribution, no matter whether the walk is noiseless or noisy. This symmetry, which is absent in the case of noiseless cyclic walk, but is restored in the presence of sufficient noise, serves as an indicator of classicalization, but only in the cyclic case. Here we show that the degree of quantum correlations between the coin and position degrees of freedom, quantified by a measure based on the disturbance induced by local measurements (Luo, Phys. Rev. A 77, 022301 (2008)), provides a suitable measure of classicalization across both type of walks. Applying this measure to compare the two walks, we find that cyclic quantum walks tend to classicalize faster than quantum walks on a line because of more efficient phase randomization due to the self-interference of the two counter-rotating waves. We model noise as acting on the coin, and given by the squeezed generalized amplitude damping (SGAD) channel, which generalizes the generalized amplitude damping channel.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
