Estimation of electrostatic interaction energies on a trapped-ion quantum computer

TL;DR

This paper demonstrates the first hardware implementation of electrostatic interaction energy calculations on a trapped-ion quantum computer, achieving chemically accurate results for a model chemical reaction.

Contribution

It introduces a method to efficiently measure electrostatic energies on quantum hardware by integrating fermionic basis rotations without increasing circuit complexity.

Findings

Electrostatic energies within chemical accuracy were obtained despite hardware noise.

Fermionic basis rotations enable efficient measurement of one-particle density matrices.

The approach reduces quantum resource requirements compared to traditional methods.

Abstract

We present the first hardware implementation of electrostatic interaction energies using a trapped-ion quantum computer. As test system for our computation, we focus on the reduction of $\mathrm{NO}$ to $\mathrm{N}_2\mathrm{O}$ catalyzed by a nitric oxide reductase (NOR). The quantum computer is used to generate an approximate ground state within the NOR active space. To efficiently measure the necessary one-particle density matrices, we incorporate fermionic basis rotations into the quantum circuit without extending the circuit length, laying the groundwork for further efficient measurement routines using factorizations. Measurements in the computational basis are then used as inputs for computing the electrostatic interaction energies on a classical computer. Our experimental results strongly agree with classical noise-less simulations of the same circuits, finding electrostatic interaction energies within chemical accuracy despite hardware noise. This work shows that algorithms tailored to specific observables of interest, such as interaction energies, may require significantly fewer quantum resources than individual ground state energies would in the straightforward supermolecular approach.