Quantum simulation of actinide chemistry: towards scalable algorithms on trapped ion quantum computers

TL;DR

This paper explores scalable quantum algorithms for actinide chemistry, demonstrating their effectiveness on ion trap quantum computers to study complex electronic structures with reduced resource requirements.

Contribution

It compares quantum computed moments and quantum phase estimation algorithms for actinide compounds and implements them on real quantum hardware with resource optimization techniques.

Findings

Quantum algorithms agree with classical calculations.

Resource reduction techniques enable practical experiments.

Successful quantum simulation of actinide energetics.

Abstract

Due to the wide range of technical applications of actinide elements, a thorough understanding of their electronic structure could complement technological improvements in many different areas. Quantum computing could greatly aid in this understanding, as it can potentially provide exponential speedups over classical approaches, thereby offering insights into the complex electronic structure of actinide compounds. As a first foray into quantum computational chemistry of actinides, this paper compares the method of quantum computed moments (QCM) as a noisy intermediate-scale quantum algorithm with a single-ancilla version of quantum phase estimation (QPE), a quantum algorithm expected to run on fault-tolerant quantum computers. We employ these algorithms to study the reaction energetics of plutonium oxides and hydrides. In order to enable quantum hardware experiments, we use several techniques to reduce resource requirements: screening individual Hamiltonian Pauli terms to reduce the measurement requirements of QCM and variational compilation to reduce the depth of QPE circuits. Finally, we derive electronic structure descriptions from a series of representative chemical models and compute the energetics from quantum experiments on Quantinuum's H-series ion trap devices using up to 19 qubits. We find our experiments to be in excellent agreement with results from classical electronic structure calculations and state vector simulations.