Subspace Variational Quantum Simulation: Fidelity Lower Bounds as Measures of Training Success

Fuente: arXiv
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Autores principales: Park, Seung, Lee, Dongkeun, Bang, Jeongho, Ryu, Hoon, Baek, Kyunghyun
Formato: Preprint
Publicado: 2025
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author Park, Seung
Lee, Dongkeun
Bang, Jeongho
Ryu, Hoon
Baek, Kyunghyun
author_facet Park, Seung
Lee, Dongkeun
Bang, Jeongho
Ryu, Hoon
Baek, Kyunghyun
contents We propose an iterative variational quantum algorithm to simulate the time evolution of arbitrary initial states within a given subspace. The algorithm compresses the Trotter circuit into a shorter-depth parameterized circuit, which is optimized simultaneously over multiple initial states in a single training process using fidelity-based cost functions. After the whole training procedure, we provide an efficiently computable lower bound on the fidelities for arbitrary states within the subspace, which guarantees the performance of the algorithm in the worst-case training scenario. We also show our cost function exhibits a barren-plateau-free region near the initial parameters at each iteration in the training landscape. The experimental demonstration of the algorithm is presented through the simulation of a 2-qubit Ising model on an IBMQ processor. As a demonstration for a larger system, a simulation of a 10-qubit Ising model is also provided.
format Preprint
id arxiv_https___arxiv_org_abs_2509_06360
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Subspace Variational Quantum Simulation: Fidelity Lower Bounds as Measures of Training Success
Park, Seung
Lee, Dongkeun
Bang, Jeongho
Ryu, Hoon
Baek, Kyunghyun
Quantum Physics
We propose an iterative variational quantum algorithm to simulate the time evolution of arbitrary initial states within a given subspace. The algorithm compresses the Trotter circuit into a shorter-depth parameterized circuit, which is optimized simultaneously over multiple initial states in a single training process using fidelity-based cost functions. After the whole training procedure, we provide an efficiently computable lower bound on the fidelities for arbitrary states within the subspace, which guarantees the performance of the algorithm in the worst-case training scenario. We also show our cost function exhibits a barren-plateau-free region near the initial parameters at each iteration in the training landscape. The experimental demonstration of the algorithm is presented through the simulation of a 2-qubit Ising model on an IBMQ processor. As a demonstration for a larger system, a simulation of a 10-qubit Ising model is also provided.
title Subspace Variational Quantum Simulation: Fidelity Lower Bounds as Measures of Training Success
topic Quantum Physics
url https://arxiv.org/abs/2509.06360