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Optimal Quantum Spatial Search with One-Dimensional Long-Range Interactions
Physical Review Letters ( IF 8.1 ) Pub Date : 2021-06-17 , DOI: 10.1103/physrevlett.126.240502
Dylan Lewis 1 , Asmae Benhemou 1 , Natasha Feinstein 1 , Leonardo Banchi 2, 3 , Sougato Bose 1
Affiliation  

Continuous-time quantum walks can be used to solve the spatial search problem, which is an essential component for many quantum algorithms that run quadratically faster than their classical counterpart, in O(n) time for n entries. However, the capability of models found in nature is largely unexplored—e.g., in one dimension only nearest-neighbor Hamiltonians have been considered so far, for which the quadratic speedup does not exist. Here, we prove that optimal spatial search, namely with O(n) run time and high fidelity, is possible in one-dimensional spin chains with long-range interactions that decay as 1/rα with distance r. In particular, near unit fidelity is achieved for α1 and, in the limit n, we find a continuous transition from a region where optimal spatial search does exist (α<1.5) to where it does not (α>1.5). Numerically, we show that spatial search is robust to dephasing noise and that, for reasonable chain lengths, α1.2 should be sufficient to demonstrate optimal spatial search experimentally with near unit fidelity.

中文翻译:

具有一维长程相互作用的最优量子空间搜索

连续时间量子游走可用于解决空间搜索问题,这是许多量子算法的基本组成部分,其运行速度比经典算法快两倍,在 (n) 的时间 n条目。然而,在自然界中发现的模型的能力在很大程度上是未开发的——例如,在一维中,到目前为止只考虑了最近邻的哈密顿量,对此不存在二次加速。在这里,我们证明了最优空间搜索,即(n) 运行时间和高保真度,在具有长程相互作用的一维自旋链中是可能的 1/rα 有距离 r. 特别是,实现了接近单位保真度α1 并且,在极限 n,我们发现从确实存在最佳空间搜索的区域开始的连续过渡(α<1.5) 到它没有的地方 (α>1.5)。在数值上,我们表明空间搜索对去相位噪声具有鲁棒性,并且对于合理的链长度,α1.2 应该足以在接近单位保真度的情况下通过实验证明最佳空间搜索。
更新日期:2021-06-17
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