Experimental parity-time symmetry quantum walks on a directed graph

Quantum walks (QW) are of crucial importance in the development of quantum information processing algorithms. Recently, several quantum algorithms have been proposed to implement network analysis, in particular to rank the centrality of nodes in networks represented by graphs. Employing QW in centra...

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Bibliographic Details
Published in:arXiv.org 2019-12
Main Authors: Wu, Tong, Izaac, J A, Zi-Xi, Li, Wang, Kai, Zhao-Zhong, Chen, Zhu, Shining, Wang, J B, Xiao-Song, Ma
Format: Article
Language:English
Subjects:
Algorithms
Data processing
Graph theory
Graphical representations
Graphs
Network analysis
Parity
Photonics
Quantum phenomena
Search engines
Symmetry
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Summary:Quantum walks (QW) are of crucial importance in the development of quantum information processing algorithms. Recently, several quantum algorithms have been proposed to implement network analysis, in particular to rank the centrality of nodes in networks represented by graphs. Employing QW in centrality ranking is advantageous comparing to certain widely used classical algorithms (e.g. PageRank) because QW approach can lift the vertex rank degeneracy in certain graphs. However, it is challenging to implement a directed graph via QW, since it corresponds to a non-Hermitian Hamiltonian and thus cannot be accomplished by conventional QW. Here we report the realizations of centrality rankings of both a three-vertex and four-vertex directed graphs with parity-time (PT) symmetric quantum walks. To achieve this, we use high-dimensional photonic quantum states, optical circuitries consisting of multiple concatenated interferometers and dimension dependent loss. Importantly, we demonstrate the advantage of QW approach experimentally by breaking the vertex rank degeneracy in a four-vertex graph. Our work shows that PT-symmetric quantum walks may be useful for realizing advanced algorithm in a quantum network.
ISSN:2331-8422
DOI:10.48550/arxiv.1912.08411