Quantum computing applied to calculations of molecular energies: CH2 benchmark

TL;DR

This paper demonstrates a quantum algorithm for calculating molecular energies, specifically benchmarking the CH2 molecule, showing potential for efficient quantum full configuration interaction calculations.

Contribution

The authors developed and tested a quantum full configuration interaction algorithm for molecular energy calculations, providing detailed implementation and performance assessment on CH2.

Findings

Quantum algorithm successfully computes CH2 electronic states.

Initial state preparation enables phase estimation in multireference cases.

Quantum approach shows promise for scalable molecular energy calculations.

Abstract

Quantum computers are appealing for their ability to solve some tasks much faster than their classical counterparts. It was shown in [Aspuru-Guzik et al., Science 309, 1704 (2005)] that they, if available, would be able to perform the full configuration interaction (FCI) energy calculations with a polynomial scaling. This is in contrast to conventional computers where FCI scales exponentially. We have developed a code for simulation of quantum computers and implemented our version of the quantum full configuration interaction algorithm. We provide a detailed description of this algorithm and the results of the assessment of its performance on the four lowest lying electronic states of CH2 molecule. This molecule was chosen as a benchmark, since its two lowest lying 1A1 states exhibit a multireference character at the equilibrium geometry. It has been shown that with a suitably chosen initial state of the quantum register, one is able to achieve the probability amplification regime of the iterative phase estimation algorithm even in this case.