Equation-of-motion variational quantum eigensolver method for computing molecular excitation energies, ionization potentials, and electron affinities

• URL: http://arxiv.org/abs/2206.10502v1
• Date: Tue, 21 Jun 2022 16:21:04 GMT
• Title: Equation-of-motion variational quantum eigensolver method for computing molecular excitation energies, ionization potentials, and electron affinities
• Authors: Ayush Asthana, Ashutosh Kumar, Vibin Abraham, Harper Grimsley, Yu Zhang, Lukasz Cincio, Sergei Tretiak, Pavel A. Dub, Sophia E. Economou, Edwin Barnes, Nicholas J. Mayhall
• Abstract summary: Near-term quantum computers are expected to facilitate material and chemical research through accurate molecular simulations. We present an equation-of-motion-based method to compute excitation energies following the variational quantum eigensolver algorithm.
• Score: 4.21608910266125
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Near-term quantum computers are expected to facilitate material and chemical research through accurate molecular simulations. Several developments have already shown that accurate ground-state energies for small molecules can be evaluated on present-day quantum devices. Although electronically excited states play a vital role in chemical processes and applications, the search for a reliable and practical approach for routine excited-state calculations on near-term quantum devices is ongoing. Inspired by excited-state methods developed for the unitary coupled-cluster theory in quantum chemistry, we present an equation-of-motion-based method to compute excitation energies following the variational quantum eigensolver algorithm for ground-state calculations on a quantum computer. We perform numerical simulations on H$_2$, H$_4$, H$_2$O, and LiH molecules to test our equation-of-motion variational quantum eigensolver (EOM-VQE) method and compare it to other current state-of-the-art methods. EOM-VQE makes use of self-consistent operators to satisfy the vacuum annihilation condition. It provides accurate and size-intensive energy differences corresponding to vertical excitation energies along with vertical ionization potentials and electron affinities. We also find that EOM-VQE is more suitable for implementation on NISQ devices, as it does not require higher than 2-body reduced density matrices and is expected to be noise-resilient.

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