Nuclear-electronic orbital molecular dynamics on quantum computers
ORAL
Abstract
Ab initio molecular dynamics (AIMD) is a well established method for the simulation of molecular systems with a wide range of applications. In many chemical systems, phenomena such as proton transfer or proton-coupled electron transfer occur, which are governed by nuclear quantum effects. These require a treatment beyond the Born-Oppenheimer (BO) approximation.
The nuclear-electronic orbital (NEO) framework [1] describes electrons and light nuclei such as protons quantum mechanically on equal footing, while heavy nuclei follow classical equations of motion (EOM) [2]. NEO thus allows to incorporate nuclear quantum effects of selected nuclei into AIMD. However, the computational effort for an exact treatment of the quantum degrees of freedom scales exponentially with the number of nuclear and electronic orbitals, restricting the applicability of the method to rather small systems.
Quantum computers offer a promising route as a scalable solver of quantum systems. Current quantum computers are affected by hardware noise, which often limits their applicability to hybrid quantum-classical methods such as the variational quantum eigensolver (VQE) [3], allowing for reduced circuit depths. With future hardware improvements, a transition towards purely quantum algorithms and scaling to large systems is expected.
We combine AIMD in the NEO framework with VQE to solve for the ground state of the quantum particles in each step of the classical EOM. The quantum forces on the classical nuclei can be evaluated on the quantum computer with additional measurements [4]. We apply the method to determine vibrational frequencies of H2 and H2O and to study proton transfer in the Zundel ion H5O2+.
[1] Webb, S. P., Iordanov, T., Hammes-Schiffer, S., J. Chem. Phys. 117, 4106 (2002)
[2] Zhao, L., Wildman, A., Tao, Z., Schneider, P., Hammes-Schiffer, S., Li, X., J. Chem. Phys. 153, 224111 (2020)
[3] Peruzzo, A., McClean, J., Shadbolt, P., Yung, M.-H., Zhou, X.-Q., Love, P. J., Aspuru-Guzik, A., O'Brien, J. L., Nat. Commun. 5, 4213 (2014)
[4] Fedorov, D. A., Otten, M. J., Gray, S. K., Alexeev, Y., J. Chem. Phys. 154, 164103 (2021)
The nuclear-electronic orbital (NEO) framework [1] describes electrons and light nuclei such as protons quantum mechanically on equal footing, while heavy nuclei follow classical equations of motion (EOM) [2]. NEO thus allows to incorporate nuclear quantum effects of selected nuclei into AIMD. However, the computational effort for an exact treatment of the quantum degrees of freedom scales exponentially with the number of nuclear and electronic orbitals, restricting the applicability of the method to rather small systems.
Quantum computers offer a promising route as a scalable solver of quantum systems. Current quantum computers are affected by hardware noise, which often limits their applicability to hybrid quantum-classical methods such as the variational quantum eigensolver (VQE) [3], allowing for reduced circuit depths. With future hardware improvements, a transition towards purely quantum algorithms and scaling to large systems is expected.
We combine AIMD in the NEO framework with VQE to solve for the ground state of the quantum particles in each step of the classical EOM. The quantum forces on the classical nuclei can be evaluated on the quantum computer with additional measurements [4]. We apply the method to determine vibrational frequencies of H2 and H2O and to study proton transfer in the Zundel ion H5O2+.
[1] Webb, S. P., Iordanov, T., Hammes-Schiffer, S., J. Chem. Phys. 117, 4106 (2002)
[2] Zhao, L., Wildman, A., Tao, Z., Schneider, P., Hammes-Schiffer, S., Li, X., J. Chem. Phys. 153, 224111 (2020)
[3] Peruzzo, A., McClean, J., Shadbolt, P., Yung, M.-H., Zhou, X.-Q., Love, P. J., Aspuru-Guzik, A., O'Brien, J. L., Nat. Commun. 5, 4213 (2014)
[4] Fedorov, D. A., Otten, M. J., Gray, S. K., Alexeev, Y., J. Chem. Phys. 154, 164103 (2021)
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Publication: Lukas Haßfurth, Juliane Heitkämper, Elias Walter, and Birger Horstmann, Nuclear-electronic orbital molecular dynamics on quantum computers (in preparation)
Presenters
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Elias Walter
- German Aerospace Center (DLR), Helmholtz Institute Ulm