论文标题
混乱对量子断层扫描中信息增益的影响
Effect of chaos on information gain in quantum tomography
论文作者
论文摘要
动力学中的混乱是否可以使量子断层扫描中的信息获得或阻碍它？我们通过考虑连续的测量断层扫描来解决这个问题，其中在量子踢顶的floquet映射的重复应用下，可观察到的Hermitian可观察到的遗传学可观察的期望值顺序获得。对于给定的动力学和Hermitian可观察物，我们观察到与随机状态相比，在良好的自旋连贯状态的断层扫描中完全相反的行为。随着动力学中的混乱的增加，自旋相干状态的重建保真度也会降低。这与先前的结果形成鲜明对比，将随机状态的层析成像与驱动系统的动力学的混乱程度联系起来。信息增益的速率，因此在断层扫描中获得的保真度不仅取决于动态中的混乱程度，以及在多大程度上导致最初可观察到的可观察到在操作员空间的各个方向上传播的程度，而且更重要的是，这些方向与密度基质的对齐程度如何。我们的研究还为运营商提供了一种操作解释，该运营商在实际的量子信息层析成像方案中就富达增长而扩散。
Does chaos in the dynamics enable information gain in quantum tomography or impede it? We address this question by considering continuous measurement tomography in which the measurement record is obtained as a sequence of expectation values of a Hermitian observable evolving under the repeated application of the Floquet map of the quantum kicked top. For a given dynamics and Hermitian observables, we observe completely opposite behavior in the tomography of well-localized spin coherent states compared to random states. As the chaos in the dynamics increases, the reconstruction fidelity of spin coherent states decreases. This contrasts with the previous results connecting information gain in tomography of random states with the degree of chaos in the dynamics that drives the system. The rate of information gain and hence the fidelity obtained in tomography depends not only on the degree of chaos in the dynamics and to what extent it causes the initial observable to spread in various directions of the operator space but, more importantly, how well these directions are aligned with the density matrix to be estimated. Our study also gives an operational interpretation for operator spreading in terms of fidelity gain in an actual quantum information tomography protocol.
