Polynomial-time quantum algorithm for the simulation of chemical dynamics

TL;DR

This paper presents a quantum algorithm that can simulate chemical reactions in polynomial time, outperforming classical methods that grow exponentially with system size, and demonstrates efficient state preparation and measurement techniques.

Contribution

The authors introduce a polynomial-time quantum algorithm for exact chemical dynamics simulation, surpassing classical exponential-time methods, and provide efficient state preparation and observable measurement strategies.

Findings

Quantum algorithms can simulate chemical reactions in polynomial time.

The approach is more accurate and faster than the Born-Oppenheimer approximation for larger systems.

Quantum computers with around 100 qubits could outperform classical computers in this task.

Abstract

The computational cost of exact methods for quantum simulation using classical computers grows exponentially with system size. As a consequence, these techniques can only be applied to small systems. By contrast, we demonstrate that quantum computers could exactly simulate chemical reactions in polynomial time. Our algorithm uses the split-operator approach and explicitly simulates all electron-nuclear and inter-electronic interactions in quadratic time. Surprisingly, this treatment is not only more accurate than the Born-Oppenheimer approximation, but faster and more efficient as well, for all reactions with more than about four atoms. This is the case even though the entire electronic wavefunction is propagated on a grid with appropriately short timesteps. Although the preparation and measurement of arbitrary states on a quantum computer is inefficient, here we demonstrate how to prepare states of chemical interest efficiently. We also show how to efficiently obtain chemically relevant observables, such as state-to-state transition probabilities and thermal reaction rates. Quantum computers using these techniques could outperform current classical computers with one hundred qubits.