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arXiv 1002.3003quant-ph
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两粒子量子游动在图同构问题中的应用

Two-particle quantum walks applied to the graph isomorphism problem

John King Gamble, Mark Friesen, Dong Zhou, Robert Joynt, S. N. Coppersmith

摘要:

我们表明,在解决一个特定的计算问题的背景下,相互作用和非相互作用的量子粒子的量子动力学是根本不同的。具体来说,我们考虑图同构问题,其中一个希望确定是否两个图是同构的(相互相关的一个重新标记的图形顶点),并专注于一类图形具有特别高的对称性称为强正则图(SRG的)。我们研究了格林函数的动态演化特征的单粒子和两粒子量子行走对非同构的SRG的,并表明,相互作用的粒子可以区分非同构的图形,非相互作用的粒子不能。我们得到了以下具体结果:(1)证明了两个非相互作用粒子(费米子或玻色子)的量子行走不能区分某些非同构的SRG对。(2)我们数值证明,两个相互作用的玻色子是更强大的比单个粒子和两个非相互作用的粒子,在量子行走的相互作用玻色子区分所有非同构对的SRG,我们检查。通过利用高吞吐量计算在进化算子之间进行超过5亿次直接比较,我们检查了所有非同构SRG的列表对,包括多达64个顶点的图。(3)通过对演化算子进行短时扩展,我们得到了区分算子,这些算子提供了对相互作用的两粒子量子行走的功率的分析见解。

英文摘要:

We show that the quantum dynamics of interacting and noninteracting quantum particles are fundamentally different in the context of solving a particular computational problem. Specifically, we consider the graph isomorphism problem, in which one wishes to determine whether two graphs are isomorphic (related to each other by a relabeling of the graph vertices), and focus on a class of graphs with particularly high symmetry called strongly regular graphs (SRG's). We study the Green's functions that characterize the dynamical evolution single-particle and two-particle quantum walks on pairs of non-isomorphic SRG's and show that interacting particles can distinguish non-isomorphic graphs that noninteracting particles cannot. We obtain the following specific results: (1) We prove that quantum walks of two noninteracting particles, Fermions or Bosons, cannot distinguish certain pairs of non-isomorphic SRG's. (2) We demonstrate numerically that two interacting Bosons are more powerful than single particles and two noninteracting particles, in that quantum walks of interacting bosons distinguish all non-isomorphic pairs of SRGs that we examined. By utilizing high-throughput computing to perform over 500 million direct comparisons between evolution operators, we checked all tabulated pairs of non-isomorphic SRGs, including graphs with up to 64 vertices. (3) By performing a short-time expansion of the evolution operator, we derive distinguishing operators that provide analytic insight into the power of the interacting two-particle quantum walk.

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