Quantum Phase Estimation Algorithm for Finding Polynomial Roots

• Main Authors: Tansuwannont Theerapat, Limkumnerd Surachate, Suwanna Sujin, Kalasuwan Pruet
• Format: Article
• Language: English
• Published: De Gruyter 2019-12-01
• Series: Open Physics
• Subjects: quantum algorithm; quantum phase estimation; eigenvalue problems; polynomial roots; 02.90.+p; 03.67.a
• Online Access: https://doi.org/10.1515/phys-2019-0087

Quantum algorithm is an algorithm for solving mathematical problems using quantum systems encoded as information, which is found to outperform classical algorithms in some specific cases. The objective of this study is to develop a quantum algorithm for finding the roots of nth degree polynomials where n is any positive integer. In classical algorithm, the resources required for solving this problem increase drastically when n increases and it would be impossible to practically solve the problem when n is large. It was found that any polynomial can be rearranged into a corresponding companion matrix, whose eigenvalues are roots of the polynomial. This leads to a possibility to perform a quantum algorithm where the number of computational resources increase as a polynomial of n. In this study, we construct a quantum circuit representing the companion matrix and use eigenvalue estimation technique to find roots of polynomial.