Non-local propagation of correlations in quantum systems with long-range interactions
Non-local propagation of correlations in quantum systems with long-range interactions
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DOI：
10.1038/nature13450
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发表时间：
2014-07-10
期刊：
影响因子：
64.8
通讯作者：
Monroe, Christopher
中科院分区：
文献类型：
--
作者：
Richerme, Philip;Gong, Zhe-Xuan;Monroe, Christopher
信息在量子多体系统中传播的最大速度直接影响到系统中不同部分的关联速度，以及系统在数值上的描述难度。对于只有短程相互作用的系统，Lieb和罗宾逊推导出了一个恒定速度的界限，将相关性限制在线性有效光锥内。然而，我们对长程相互作用系统的传播速度知之甚少，因为最佳长程边界太松，无法为任何已知的自旋模型给出正确的光锥形状，而且解析解很少存在。在这项工作中，我们实验确定的空间和时间依赖的相关性的远离平衡的量子多体系统下的远程伊辛或XY模型哈密顿演化。对于几个不同的相互作用范围，我们提取的光锥的形状和测量的相关性传播通过系统的速度。在许多情况下，我们发现增加的传播速度，这违反了Lieb-Robinson预测，在一个实例中，不能用任何现有的理论来解释。我们的研究结果表明，即使是中等大小的量子模拟器也可以很好地用于研究复杂的多体系统，这些系统对经典计算来说是难以处理的。
The maximum speed with which information can propagate in a quantum many-body system directly affects how quickly disparate parts of the system can become correlated and how difficult the system will be to describe numerically. For systems with only short-range interactions, Lieb and Robinson derived a constant-velocity bound that limits correlations to within a linear effective light cone. However, little is known about the propagation speed in systems with long-range interactions, since the best long-range bound is too loose to give the correct light-cone shape for any known spin model and since analytic solutions rarely exist. In this work, we experimentally determine the spatial and time-dependent correlations of a far-from-equilibrium quantum many-body system evolving under a long-range Ising- or XY-model Hamiltonian. For several different interaction ranges, we extract the shape of the light cone and measure the velocity with which correlations propagate through the system. In many cases we find increasing propagation velocities, which violate the Lieb-Robinson prediction, and in one instance cannot be explained by any existing theory. Our results demonstrate that even modestly-sized quantum simulators are well-poised for studying complicated many-body systems that are intractable to classical computation.