Efficient Simulation of Quantum Chemistry Problems in an Enlarged Basis Set

We propose a quantum algorithm to simulate the dynamics in quantum chemistry problems. It is based on adding fresh qubits at each Trotter step, which enables a simpler implementation of the dynamics in the extended system. After each step, the extra qubits are recycled, so that the whole process acc...

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Main Authors: Maxine Luo, J. Ignacio Cirac
Format: Article
Language:English
Published: American Physical Society 2025-03-01
Series:PRX Quantum
Online Access:http://doi.org/10.1103/PRXQuantum.6.010355
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author Maxine Luo
J. Ignacio Cirac
author_facet Maxine Luo
J. Ignacio Cirac
author_sort Maxine Luo
collection DOAJ
description We propose a quantum algorithm to simulate the dynamics in quantum chemistry problems. It is based on adding fresh qubits at each Trotter step, which enables a simpler implementation of the dynamics in the extended system. After each step, the extra qubits are recycled, so that the whole process accurately approximates the correct unitary evolution. A key ingredient of the approach is an isometry that maps a simple diagonal Hamiltonian in the extended system to the original one, and we give a procedure to compute this isometry. We estimate the error at each time step, as well as the number of gates, which scales as O(N^{2}), where N is the number of orbitals. We illustrate our results with three examples: the hydrogen chain, small molecules, and the FeMoco (Fe_{7}MoS_{9}C) molecule. In the hydrogen chain and the hydrogen molecule, we observe that the error scales in the same way as the Trotter error. For FeMoco, we estimate the number of gates in a fault-tolerant setup.
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institution Kabale University
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spelling doaj-art-69cd8d2519d8438c8b359a4df39d0bae2025-08-20T03:39:49ZengAmerican Physical SocietyPRX Quantum2691-33992025-03-016101035510.1103/PRXQuantum.6.010355Efficient Simulation of Quantum Chemistry Problems in an Enlarged Basis SetMaxine LuoJ. Ignacio CiracWe propose a quantum algorithm to simulate the dynamics in quantum chemistry problems. It is based on adding fresh qubits at each Trotter step, which enables a simpler implementation of the dynamics in the extended system. After each step, the extra qubits are recycled, so that the whole process accurately approximates the correct unitary evolution. A key ingredient of the approach is an isometry that maps a simple diagonal Hamiltonian in the extended system to the original one, and we give a procedure to compute this isometry. We estimate the error at each time step, as well as the number of gates, which scales as O(N^{2}), where N is the number of orbitals. We illustrate our results with three examples: the hydrogen chain, small molecules, and the FeMoco (Fe_{7}MoS_{9}C) molecule. In the hydrogen chain and the hydrogen molecule, we observe that the error scales in the same way as the Trotter error. For FeMoco, we estimate the number of gates in a fault-tolerant setup.http://doi.org/10.1103/PRXQuantum.6.010355
spellingShingle Maxine Luo
J. Ignacio Cirac
Efficient Simulation of Quantum Chemistry Problems in an Enlarged Basis Set
PRX Quantum
title Efficient Simulation of Quantum Chemistry Problems in an Enlarged Basis Set
title_full Efficient Simulation of Quantum Chemistry Problems in an Enlarged Basis Set
title_fullStr Efficient Simulation of Quantum Chemistry Problems in an Enlarged Basis Set
title_full_unstemmed Efficient Simulation of Quantum Chemistry Problems in an Enlarged Basis Set
title_short Efficient Simulation of Quantum Chemistry Problems in an Enlarged Basis Set
title_sort efficient simulation of quantum chemistry problems in an enlarged basis set
url http://doi.org/10.1103/PRXQuantum.6.010355
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AT jignaciocirac efficientsimulationofquantumchemistryproblemsinanenlargedbasisset