Efficient quantum computation of molecular forces and other energy gradients

While most work on the quantum simulation of chemistry has focused on computing energy surfaces, a similarly important application requiring subtly different algorithms is the computation of energy derivatives. Almost all molecular properties can be expressed an energy derivative, including molecula...

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Main Authors: Thomas E. O'Brien, Michael Streif, Nicholas C. Rubin, Raffaele Santagati, Yuan Su, William J. Huggins, Joshua J. Goings, Nikolaj Moll, Elica Kyoseva, Matthias Degroote, Christofer S. Tautermann, Joonho Lee, Dominic W. Berry, Nathan Wiebe, Ryan Babbush
Format: Article
Language:English
Published: American Physical Society 2022-12-01
Series:Physical Review Research
Online Access:http://doi.org/10.1103/PhysRevResearch.4.043210
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author Thomas E. O'Brien
Michael Streif
Nicholas C. Rubin
Raffaele Santagati
Yuan Su
William J. Huggins
Joshua J. Goings
Nikolaj Moll
Elica Kyoseva
Matthias Degroote
Christofer S. Tautermann
Joonho Lee
Dominic W. Berry
Nathan Wiebe
Ryan Babbush
author_facet Thomas E. O'Brien
Michael Streif
Nicholas C. Rubin
Raffaele Santagati
Yuan Su
William J. Huggins
Joshua J. Goings
Nikolaj Moll
Elica Kyoseva
Matthias Degroote
Christofer S. Tautermann
Joonho Lee
Dominic W. Berry
Nathan Wiebe
Ryan Babbush
author_sort Thomas E. O'Brien
collection DOAJ
description While most work on the quantum simulation of chemistry has focused on computing energy surfaces, a similarly important application requiring subtly different algorithms is the computation of energy derivatives. Almost all molecular properties can be expressed an energy derivative, including molecular forces, which are essential for applications such as molecular dynamics simulations. Here, we introduce new quantum algorithms for computing molecular energy derivatives with significantly lower complexity than prior methods. Under cost models appropriate for noisy-intermediate scale quantum devices, we demonstrate how low-rank factorization and other tomography schemes can be optimized for energy derivative calculations. We numerically demonstrate that our techniques reduce the number of circuit repetitions required by many orders of magnitude for even modest systems, and that the cost of estimating an entire force vector may in some systems be lower than the cost of estimating the energy. In the context of fault-tolerant algorithms, we develop new methods of estimating energy derivatives with Heisenberg limited scaling, incorporating state-of-the-art techniques for block encoding fermionic operators. In contrast to our near-term results, we find that the cost of estimating forces with any of our Heisenberg-limited methods is bounded by the cost of estimating energies, due to inner loops requiring either energy estimation or reflections around the ground state. This implies that applications such as geometry optimization, coupling parameter estimation, and spectral prediction may be practical on fault-tolerant quantum devices, but tractable molecular dynamics simulations of large-scale systems requires further algorithmic advances.
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spelling doaj.art-5cede1d0c45840d6b4389cabde88e8f92024-04-12T17:27:17ZengAmerican Physical SocietyPhysical Review Research2643-15642022-12-014404321010.1103/PhysRevResearch.4.043210Efficient quantum computation of molecular forces and other energy gradientsThomas E. O'BrienMichael StreifNicholas C. RubinRaffaele SantagatiYuan SuWilliam J. HugginsJoshua J. GoingsNikolaj MollElica KyosevaMatthias DegrooteChristofer S. TautermannJoonho LeeDominic W. BerryNathan WiebeRyan BabbushWhile most work on the quantum simulation of chemistry has focused on computing energy surfaces, a similarly important application requiring subtly different algorithms is the computation of energy derivatives. Almost all molecular properties can be expressed an energy derivative, including molecular forces, which are essential for applications such as molecular dynamics simulations. Here, we introduce new quantum algorithms for computing molecular energy derivatives with significantly lower complexity than prior methods. Under cost models appropriate for noisy-intermediate scale quantum devices, we demonstrate how low-rank factorization and other tomography schemes can be optimized for energy derivative calculations. We numerically demonstrate that our techniques reduce the number of circuit repetitions required by many orders of magnitude for even modest systems, and that the cost of estimating an entire force vector may in some systems be lower than the cost of estimating the energy. In the context of fault-tolerant algorithms, we develop new methods of estimating energy derivatives with Heisenberg limited scaling, incorporating state-of-the-art techniques for block encoding fermionic operators. In contrast to our near-term results, we find that the cost of estimating forces with any of our Heisenberg-limited methods is bounded by the cost of estimating energies, due to inner loops requiring either energy estimation or reflections around the ground state. This implies that applications such as geometry optimization, coupling parameter estimation, and spectral prediction may be practical on fault-tolerant quantum devices, but tractable molecular dynamics simulations of large-scale systems requires further algorithmic advances.http://doi.org/10.1103/PhysRevResearch.4.043210
spellingShingle Thomas E. O'Brien
Michael Streif
Nicholas C. Rubin
Raffaele Santagati
Yuan Su
William J. Huggins
Joshua J. Goings
Nikolaj Moll
Elica Kyoseva
Matthias Degroote
Christofer S. Tautermann
Joonho Lee
Dominic W. Berry
Nathan Wiebe
Ryan Babbush
Efficient quantum computation of molecular forces and other energy gradients
Physical Review Research
title Efficient quantum computation of molecular forces and other energy gradients
title_full Efficient quantum computation of molecular forces and other energy gradients
title_fullStr Efficient quantum computation of molecular forces and other energy gradients
title_full_unstemmed Efficient quantum computation of molecular forces and other energy gradients
title_short Efficient quantum computation of molecular forces and other energy gradients
title_sort efficient quantum computation of molecular forces and other energy gradients
url http://doi.org/10.1103/PhysRevResearch.4.043210
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