Scalable Quantum Simulation of Molecular Energies

TL;DR

This paper demonstrates the first scalable quantum simulation of molecular energies on a superconducting qubit platform, using two algorithms to accurately compute the energy surface of hydrogen, highlighting the potential of variational quantum methods.

Contribution

It presents the first experimental implementation of quantum algorithms for molecular energy calculations without exponential precompilation, showcasing the viability of variational quantum eigensolvers for chemistry.

Findings

VQE predicts dissociation energy within chemical accuracy.

Quantum phase estimation demonstrates accurate energy measurement.

VQE shows robustness to certain quantum errors.

Abstract

We report the first electronic structure calculation performed on a quantum computer without exponentially costly precompilation. We use a programmable array of superconducting qubits to compute the energy surface of molecular hydrogen using two distinct quantum algorithms. First, we experimentally execute the unitary coupled cluster method using the variational quantum eigensolver. Our efficient implementation predicts the correct dissociation energy to within chemical accuracy of the numerically exact result. Second, we experimentally demonstrate the canonical quantum algorithm for chemistry, which consists of Trotterization and quantum phase estimation. We compare the experimental performance of these approaches to show clear evidence that the variational quantum eigensolver is robust to certain errors. This error tolerance inspires hope that variational quantum simulations of classically intractable molecules may be viable in the near future.