Bang-bang preparation of a quantum many-body ground state in a finite lattice: optimization of the algorithm with a tensor network

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Autori principali: Sokolov, Ihor, Dziarmaga, Jacek
Natura: Preprint
Pubblicazione: 2025
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author Sokolov, Ihor
Dziarmaga, Jacek
author_facet Sokolov, Ihor
Dziarmaga, Jacek
contents A bang-bang (BB) algorithm prepares the ground state of a lattice quantum many-body Hamiltonian $H=H_1+H_2$ by evolving an initial product state alternating between $H_1$ and $H_2$. We optimize the algorithm with tensor networks in one and two dimensions. The optimization has two stages. In stage one, a shallow translationally-invariant circuit is optimized in an infinite lattice. In stage two, the infinite-lattice gate sequence is used as a starting point for a finite lattice where it remains optimal in the bulk. The prepared state requires optimization only at its boundary, within a healing length from lattice edges, and the gate sequence needs to be modified only within the causal cone of the boundary. We test the procedure in the 1D and 2D quantum Ising model near its quantum critical point employing, respectively, the matrix product state (MPS) and the pair-entangled projected state (PEPS). At the boundary already the infinite-lattice sequence turns out to provide a more accurate state than in the bulk.
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id arxiv_https___arxiv_org_abs_2505_08226
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Bang-bang preparation of a quantum many-body ground state in a finite lattice: optimization of the algorithm with a tensor network
Sokolov, Ihor
Dziarmaga, Jacek
Quantum Physics
Quantum Gases
A bang-bang (BB) algorithm prepares the ground state of a lattice quantum many-body Hamiltonian $H=H_1+H_2$ by evolving an initial product state alternating between $H_1$ and $H_2$. We optimize the algorithm with tensor networks in one and two dimensions. The optimization has two stages. In stage one, a shallow translationally-invariant circuit is optimized in an infinite lattice. In stage two, the infinite-lattice gate sequence is used as a starting point for a finite lattice where it remains optimal in the bulk. The prepared state requires optimization only at its boundary, within a healing length from lattice edges, and the gate sequence needs to be modified only within the causal cone of the boundary. We test the procedure in the 1D and 2D quantum Ising model near its quantum critical point employing, respectively, the matrix product state (MPS) and the pair-entangled projected state (PEPS). At the boundary already the infinite-lattice sequence turns out to provide a more accurate state than in the bulk.
title Bang-bang preparation of a quantum many-body ground state in a finite lattice: optimization of the algorithm with a tensor network
topic Quantum Physics
Quantum Gases
url https://arxiv.org/abs/2505.08226