Two Quantum Algorithms for Nonlinear Reaction-Diffusion Equation using Chebyshev Approximation Method

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Auteur principal: Kumar, Manish
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Publié: 2025
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author Kumar, Manish
author_facet Kumar, Manish
contents We present two new quantum algorithms for reaction-diffusion equations that employ the truncated Chebyshev polynomial approximation. This method is employed to numerically solve the ordinary differential equation emerging from the linearization of the associated nonlinear differential equation. In the first algorithm, we use the matrix exponentiation method (Patel et al., 2018), while in the second algorithm, we repurpose the quantum spectral method (Childs et al., 2020). Our main technical contribution is to derive the sufficient conditions for the diagonalization of the Carleman embedding matrix, which is indispensable for designing both quantum algorithms. We supplement this with an efficient iterative algorithm to diagonalize the Carleman matrix. Our first algorithm has gate complexity of O(d$\cdot$log(d)+T$\cdot$polylog(T/$\varepsilon$)). Here $d$ is the size of the Carleman matrix, $T$ is the simulation time, and $\varepsilon$ is the approximation error. The second algorithm is polynomial in $log(d)$, $T$, and $log(1/\varepsilon)$ - the gate complexity scales as O(polylog(d)$\cdot$T$\cdot$polylog(T/$\varepsilon$)). In terms of $T$ and $\varepsilon$, this is comparable to the speedup gained by the current best known quantum algorithm for this problem, the truncated Taylor series method (Costa et.al., 2025). Our approach has two shortcomings. First, we have not provided an upper bound, in terms of d, on the condition number of the Carleman matrix. Second, the success of the diagonalization is based on a conjecture that a specific trigonometric equation has no integral solution. However, we provide strategies to mitigate these shortcomings in most practical cases.
format Preprint
id arxiv_https___arxiv_org_abs_2510_19855
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Two Quantum Algorithms for Nonlinear Reaction-Diffusion Equation using Chebyshev Approximation Method
Kumar, Manish
Quantum Physics
Pattern Formation and Solitons
Computational Physics
We present two new quantum algorithms for reaction-diffusion equations that employ the truncated Chebyshev polynomial approximation. This method is employed to numerically solve the ordinary differential equation emerging from the linearization of the associated nonlinear differential equation. In the first algorithm, we use the matrix exponentiation method (Patel et al., 2018), while in the second algorithm, we repurpose the quantum spectral method (Childs et al., 2020). Our main technical contribution is to derive the sufficient conditions for the diagonalization of the Carleman embedding matrix, which is indispensable for designing both quantum algorithms. We supplement this with an efficient iterative algorithm to diagonalize the Carleman matrix. Our first algorithm has gate complexity of O(d$\cdot$log(d)+T$\cdot$polylog(T/$\varepsilon$)). Here $d$ is the size of the Carleman matrix, $T$ is the simulation time, and $\varepsilon$ is the approximation error. The second algorithm is polynomial in $log(d)$, $T$, and $log(1/\varepsilon)$ - the gate complexity scales as O(polylog(d)$\cdot$T$\cdot$polylog(T/$\varepsilon$)). In terms of $T$ and $\varepsilon$, this is comparable to the speedup gained by the current best known quantum algorithm for this problem, the truncated Taylor series method (Costa et.al., 2025). Our approach has two shortcomings. First, we have not provided an upper bound, in terms of d, on the condition number of the Carleman matrix. Second, the success of the diagonalization is based on a conjecture that a specific trigonometric equation has no integral solution. However, we provide strategies to mitigate these shortcomings in most practical cases.
title Two Quantum Algorithms for Nonlinear Reaction-Diffusion Equation using Chebyshev Approximation Method
topic Quantum Physics
Pattern Formation and Solitons
Computational Physics
url https://arxiv.org/abs/2510.19855