Compact quantum circuits for variational calculations of ro-vibrational energy levels of molecules on a quantum computer

• URL: http://arxiv.org/abs/2303.09822v1
• Date: Fri, 17 Mar 2023 08:02:38 GMT
• Title: Compact quantum circuits for variational calculations of ro-vibrational energy levels of molecules on a quantum computer
• Authors: K. Asnaashari, R. V. Krems
• Abstract summary: We show a general approach to computing the ro-vibrational energy levels of molecules by combining the discrete variable representation of molecular Hamiltonians with variational quantum eigensolvers and a greedy search of gate permutations. To illustrate the generality and adaptability of this approach, we compute the vibrational energy levels of Cr-NH in seven electronic states as well as the vibrational energy levels of van der Waals ArHCl and Mg-HCl.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: While quantum computing algorithms have been successfully applied to electronic structure of molecules, applications of quantum computing to molecular dynamics remain scarce. The variability of intra-molecular interaction potentials gives rise to vibrational states with a wide range of properties. It is therefore challenging to obtain a general representation of molecular ro-vibrational states by states of a quantum computer with a limited number of qubits and quantum gates. We demonstrate a general approach to computing the ro-vibrational energy levels of molecules by combining the discrete variable representation of molecular Hamiltonians with variational quantum eigensolvers and a greedy search of gate permutations, yielding accurate representations of both ground and excited vibrational states by compact quantum circuits with a small number of gates. To illustrate the generality and adaptability of this approach, we compute the vibrational energy levels of Cr$_2$ in seven electronic states as well as the vibrational energy levels of van der Waals complexes Ar-HCl and Mg-NH, illustrating that accuracy of 1 cm$^{-1}$ can be achieved with between 2 and 9 entangling gates.

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