Quantum Simulation of Non-Unitary Dynamics via Amplitude-Phase Separation

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Hauptverfasser: Hu, Qitong, Jin, Shi
Format: Preprint
Veröffentlicht: 2026
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author Hu, Qitong
Jin, Shi
author_facet Hu, Qitong
Jin, Shi
contents Linear non-unitary dynamics arise in open quantum systems, non-Hermitian models, and numerical evolution problems, yet current quantum algorithms do not cleanly separate coherent and dissipative effects at the design level. We introduce Amplitude-Phase Separation (APS), a decomposition framework with two complementary forms: phase-driven APS isolates the unitary component and maps the remainder to a Hermitian problem, whereas amplitude-driven APS extracts the Hermitian component and treats the remaining interaction separately. For time-independent dynamics, the two routes capture complementary advantages within one framework: phase-driven APS yields additive rather than multiplicative tolerance dependence, while amplitude-driven APS yields square-root dissipative scaling in multiscale regimes. APS also provides a unified interpretation of representative methods, including LCHS (Linear Combination of Hamiltonian Simulation) and NDME (Non-Diagonal Density Matrix Encoding), and clarifies where coherent and dissipative bottlenecks enter non-unitary simulation. The benchmarks confirm the predicted crossover between phase-driven and amplitude-driven advantages in advection-diffusion and Bloch-relaxation models.
format Preprint
id arxiv_https___arxiv_org_abs_2602_09575
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Quantum Simulation of Non-Unitary Dynamics via Amplitude-Phase Separation
Hu, Qitong
Jin, Shi
Quantum Physics
Mathematical Physics
Linear non-unitary dynamics arise in open quantum systems, non-Hermitian models, and numerical evolution problems, yet current quantum algorithms do not cleanly separate coherent and dissipative effects at the design level. We introduce Amplitude-Phase Separation (APS), a decomposition framework with two complementary forms: phase-driven APS isolates the unitary component and maps the remainder to a Hermitian problem, whereas amplitude-driven APS extracts the Hermitian component and treats the remaining interaction separately. For time-independent dynamics, the two routes capture complementary advantages within one framework: phase-driven APS yields additive rather than multiplicative tolerance dependence, while amplitude-driven APS yields square-root dissipative scaling in multiscale regimes. APS also provides a unified interpretation of representative methods, including LCHS (Linear Combination of Hamiltonian Simulation) and NDME (Non-Diagonal Density Matrix Encoding), and clarifies where coherent and dissipative bottlenecks enter non-unitary simulation. The benchmarks confirm the predicted crossover between phase-driven and amplitude-driven advantages in advection-diffusion and Bloch-relaxation models.
title Quantum Simulation of Non-Unitary Dynamics via Amplitude-Phase Separation
topic Quantum Physics
Mathematical Physics
url https://arxiv.org/abs/2602.09575