The electronic complexity of the ground-state of the FeMo cofactor of nitrogenase as relevant to quantum simulations

TL;DR

This paper challenges a recent model of the FeMo cofactor's electronic structure used in quantum simulations, emphasizing the importance of accurate active space selection for reliable classical and quantum resource estimates.

Contribution

It introduces a revised active space model for the FeMo cofactor that better captures its electronic structure, aiding future benchmarking and simulation efforts.

Findings

The previous active space model was not representative of the ground-state electronic structure.

A new active space model is proposed that includes the essential open-shell character.

Classical simulation complexity estimates should not rely on the previous model.

Abstract

We report that a recent active space model of the nitrogenase FeMo cofactor, proposed in the context of quantum simulations, is not representative of the electronic structure of the FeMo cofactor ground-state. Although quantum resource estimates, outside of the cost of adiabatic state preparation, will not be much affected, conclusions should not be drawn from the complexity of classical simulations of the electronic structure of this system in this active space. We provide a different model active space for the FeMo cofactor that contains the basic open-shell qualitative character, which may be useful as a benchmark system for making classical and quantum resource estimates.