Quantum circuit representation of Bayesian networks Sima E. Borujenia, Saideep Nannapanenia,∗, Nam H. Nguyenb,1, Elizabeth C. Behrmanb, James E. Steckc aDepartment of Industrial, Systems, and Manufacturing Engineering, Wichita State University 1845 Fairmount St, Box 35, Wichita, KS, 67260 USA
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[email protected] bDepartment of Mathematics, Statistics, and Physics, Wichita State University 1845 Fairmount St, Box 33, Wichita, KS, 67260 USA
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[email protected] cDepartment of Aerospace Engineering, Wichita State University 1845 Fairmount St, Box 44, Wichita, KS, 67260 USA
[email protected] Abstract Probabilistic graphical models such as Bayesian networks are widely used to model stochastic systems to perform various types of analysis such as proba- bilistic prediction, risk analysis, and system health monitoring, which can be- come computationally expensive in large-scale systems. While demonstrations of true quantum supremacy remain rare, quantum computing applications man- aging to exploit the advantages of amplitude amplification have shown signifi- cant computational benefits when compared against their classical counterparts. We develop a systematic method for designing a quantum circuit to represent a generic discrete Bayesian network with nodes that may have two or more states, where nodes with more than two states are mapped to multiple qubits. The marginal probabilities associated with root nodes (nodes without any par- ent nodes) are represented using rotation gates, and the conditional probability arXiv:2004.14803v2 [quant-ph] 12 Apr 2021 tables associated with non-root nodes are represented using controlled rota- tion gates. The controlled rotation gates with more than one control qubit are represented using ancilla qubits.