Chemistry Beyond the Scale of Exact Diagonalization on a Quantum-Centric Supercomputer

TL;DR

This paper demonstrates a hybrid quantum-classical approach using a supercomputer and a quantum processor to simulate complex chemical systems with up to 77 qubits, surpassing traditional exact methods.

Contribution

It introduces a distributed computing framework that offloads most quantum computations, enabling the simulation of larger quantum chemistry problems than previously possible.

Findings

Successfully simulated N₂ dissociation and iron-sulfur clusters with up to 77 qubits.

Produced upper bounds for ground-state energies and approximations to wavefunctions.

Showed that quantum-centric supercomputing can handle chemistry problems beyond exact diagonalization.

Abstract

A universal quantum computer can simulate diverse quantum systems, with electronic structure for chemistry offering challenging problems for practical use cases around the hundred-qubit mark. While current quantum processors have reached this size, deep circuits and large number of measurements lead to prohibitive runtimes for quantum computers in isolation. Here, we demonstrate the use of classical distributed computing to offload all but an intrinsically quantum component of a workflow for electronic structure simulations. Using a Heron superconducting processor and the supercomputer Fugaku, we simulate the ground-state dissociation of N$_2$ and the [2Fe-2S] and [4Fe-4S] clusters, with circuits up to 77 qubits and 10,570 gates. The proposed algorithm processes quantum samples to produce upper bounds for the ground-state energy and sparse approximations to the ground-state wavefunctions. Our results suggest that, for current error rates, a quantum-centric supercomputing architecture can tackle challenging chemistry problems beyond sizes amenable to exact diagonalization.