论文标题
线性光锥的层次结构,具有远距离相互作用
Hierarchy of linear light cones with long-range interactions
论文作者
论文摘要
在具有局部相互作用的量子多体系统中,量子信息和纠缠无法在线性光锥之外散布,该线性光锥以类似于光速的新兴速度扩展。在足够分开的时空点处的本地操作大约上下班 - 给定多体状态,$ \ MATHCAL {O} _X(T)\ MATHCAL {O} _Y |ψ\ rangle \ rangle \ rangle \ langle \ langle \ ailtcal {o} $ | x-y | \ gtrsim vt $,其中$ v $是有限的。然而,大多数在自然界中实现的非权威性物理系统具有长期相互作用:两个自由度与距离$ r $与势能$ v(r)\ propto 1/r^α$相互作用。在具有远距离相互作用的系统中,我们严格地建立了线性光锥的层次结构:在相同的$α$下,某些量子信息处理任务受线性光锥的约束,而其他量子却没有。在一个空间尺寸中,当$α> 3 $(Lieb-Robinson Light锥)时,每个多体状态都存在此线性光锥。对于典型的状态,当$α> \ frac {5} {2} $(Frobenius Light锥)时,从希尔伯特空间随机选择了均匀的状态;对于$α> 2 $(自由灯锥)时,对于非相互作用系统的每个状态。这些界限适用于时间依赖的系统,最佳选择是亚代词的改进。我们关于Lieb-Robinson和Free Light锥及其紧密度的定理也将其推广到任意维度。我们讨论了界限对连接相关器和拓扑顺序增长的含义,间隙系统中相关性的聚类以及具有远距离相互作用的系统的数字模拟。此外,我们表明,通用量子状态转移以及多体量子混乱是由Frobenius Light锥界的,因此受所有Lieb-Robinson边界的约束。
In quantum many-body systems with local interactions, quantum information and entanglement cannot spread outside of a linear light cone, which expands at an emergent velocity analogous to the speed of light. Local operations at sufficiently separated spacetime points approximately commute -- given a many-body state, $\mathcal{O}_x(t) \mathcal{O}_y |ψ\rangle \approx \mathcal{O}_y\mathcal{O}_x(t) |ψ\rangle$ with arbitrarily small errors -- so long as $|x-y|\gtrsim vt$, where $v$ is finite. Yet most non-relativistic physical systems realized in nature have long-range interactions: two degrees of freedom separated by a distance $r$ interact with potential energy $V(r) \propto 1/r^α$. In systems with long-range interactions, we rigorously establish a hierarchy of linear light cones: at the same $α$, some quantum information processing tasks are constrained by a linear light cone while others are not. In one spatial dimension, this linear light cone exists for every many-body state when $α>3$ (Lieb-Robinson light cone); for a typical state chosen uniformly at random from the Hilbert space when $α>\frac{5}{2}$ (Frobenius light cone); for every state of a non-interacting system when $α>2$ (free light cone). These bounds apply to time-dependent systems and are optimal up to subalgebraic improvements. Our theorems regarding the Lieb-Robinson and free light cones -- and their tightness -- also generalize to arbitrary dimensions. We discuss the implications of our bounds on the growth of connected correlators and of topological order, the clustering of correlations in gapped systems, and the digital simulation of systems with long-range interactions. In addition, we show that universal quantum state transfer, as well as many-body quantum chaos, are bounded by the Frobenius light cone, and therefore are poorly constrained by all Lieb-Robinson bounds.