A Domain-agnostic, Noise-resistant, Hardware-efficient Evolutionary Variational Quantum Eigensolver

TL;DR

This paper introduces EVQE, a versatile, noise-resistant, and hardware-efficient evolutionary algorithm for variational quantum eigensolvers that outperforms traditional methods in accuracy, circuit depth, and gate count across simulated and real quantum hardware.

Contribution

The paper presents EVQE, a novel evolutionary approach to generate and optimize variational ansatzes, improving general applicability, efficiency, and noise robustness over existing VQE methods.

Findings

EVQE produces shallower ansatz circuits with fewer CX gates than traditional VQE.

EVQE demonstrates at least 3.6x less error in noisy simulations compared to VQE.

EVQE successfully runs on a real 5-qubit IBMQ quantum computer.

Abstract

Variational quantum algorithms have shown promise in numerous fields due to their versatility in solving problems of scientific and commercial interest. However, leading algorithms for Hamiltonian simulation, such as the Variational Quantum Eigensolver (VQE), use fixed preconstructed ansatzes, limiting their general applicability and accuracy. Thus, variational forms---the quantum circuits that implement ansatzes ---are either crafted heuristically or by encoding domain-specific knowledge. In this paper, we present an Evolutionary Variational Quantum Eigensolver (EVQE), a novel variational algorithm that uses evolutionary programming techniques to minimize the expectation value of a given Hamiltonian by dynamically generating and optimizing an ansatz. The algorithm is equally applicable to optimization problems in all domains, obtaining accurate energy evaluations with hardware-efficient ansatzes. In molecular simulations, the variational forms generated by EVQE are up to $18.6\times$ shallower and use up to $12\times$ fewer CX gates than those obtained by VQE with a unitary coupled cluster ansatz. EVQE demonstrates significant noise-resistance properties, obtaining results in noisy simulation with at least $3.6\times$ less error than VQE using any tested ansatz configuration. We successfully evaluated EVQE on a real 5-qubit IBMQ quantum computer. The experimental results, which we obtained both via simulation and on real quantum hardware, demonstrate the effectiveness of EVQE for general-purpose optimization on the quantum computers of the present and near future.