Overlap-ADAPT-VQE: Practical Quantum Chemistry on Quantum Computers via Overlap-Guided Compact Ans\"atze

TL;DR

This paper introduces Overlap-ADAPT-VQE, a novel quantum algorithm that constructs ultra-compact wave-function ansätze by maximizing overlap with target states, significantly improving efficiency and accuracy in quantum chemistry simulations on near-term quantum computers.

Contribution

The paper presents Overlap-ADAPT-VQE, a new method that avoids local minima by using overlap maximization, leading to more compact ansätze and better performance for strongly correlated systems.

Findings

Achieves substantial circuit depth savings in strongly correlated systems

Produces ultra-compact ansätze suitable for high-accuracy initializations

Enables simulations of larger systems with classical target wave-functions

Abstract

ADAPT-VQE is a robust algorithm for hybrid quantum-classical simulations of quantum chemical systems on near-term quantum computers. While its iterative process systematically reaches the ground state energy, ADAPT-VQE is sensitive to local energy minima, leading to over-parameterized ans\"atze. We introduce the Overlap-ADAPT-VQE to grow wave-functions by maximizing their overlap with any intermediate target wave-function that already captures some electronic correlation. By avoiding building the ansatz in the energy landscape strewn with local minima, the Overlap-ADAPT-VQE produces ultra-compact ans\"atze suitable for high-accuracy initializations of a new ADAPT procedure. Spectacular advantages over ADAPT-VQE are observed for strongly correlated systems including massive savings in circuit depth. Since this compression strategy can also be initialized with accurate Selected-Configuration Interaction (SCI) classical target wave-functions, it paves the way for chemically accurate simulations of larger systems, and strengthens the promise of decisively surpassing classical quantum chemistry through the power of quantum computing.