长程相互作用量子系统中的准局域性保护
Protected quasi-locality in quantum systems with long-range interactions
摘要：
我们研究具有长程相互作用的量子系统的非平衡动力学。两种不同的模型描述，分别被认为是相互作用的格子玻色子和自旋。我们的研究依赖于一种基于精确的多体数值计算以及准粒子微观理论的综合方法。对于足够快衰减的长程势，我们发现长程Lieb-Robinson边界所设定的量子速度极限是永远无法达到的，并且发现了一种纯粹的弹道行为;对于慢衰减势，我们观察到一种完全不同的情形。在玻色子的情况下，一个显着的局部相关性的传播仍然被观察到，尽管在系统中的无限快速旅行的激发的存在。这与自旋情况形成鲜明对比，自旋情况下局域性被破坏。最后，我们提供了一个微观的理由观察到的不同制度和起源的玻色子模型中的受保护的地方。
英文摘要：
We study the out-of-equilibrium dynamics of quantum systems with long-range interactions. Two different models describing, respectively, interacting lattice bosons and spins are considered. Our study relies on a combined approach based on accurate many-body numerical calculations as well as on a quasiparticle microscopic theory. For sufficiently fast decaying long-range potentials, we find that the quantum speed limit set by the long-range Lieb-Robinson bounds is never attained and a purely ballistic behavior is found. For slowly decaying potentials, a radically different scenario is observed. In the bosonic case, a remarkable local spreading of correlations is still observed, despite the existence of infinitely fast traveling excitations in the system. This is in marked contrast to the spin case, where locality is broken. We finally provide a microscopic justification of the different regimes observed and of the origin of the protected locality in the bosonic model.
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