Operator-Projected Variational Quantum Imaginary Time Evolution

TL;DR

This paper introduces an optimized variational quantum imaginary time evolution method that reduces circuit depth and measurement complexity, enabling more efficient ground state preparation on quantum computers.

Contribution

It proposes a projection-based approach to simplify VQITE, significantly decreasing circuit depth and measurement requirements compared to existing methods.

Findings

Achieves twofold circuit depth reduction

Reduces measurement complexity from quadratic to linear

Demonstrates significant measurement efficiency improvements in simulations

Abstract

Variational Quantum Imaginary Time Evolution (VQITE) is a leading technique for ground state preparation on quantum computers. A significant computational challenge of VQITE is the determination of the quantum geometric tensor. We show that requiring the imaginary-time evolution to be correct only when projected onto a chosen set of operators allows to achieve a twofold reduction in circuit depth by bypassing fidelity estimations, and reduces measurement complexity from quadratic to linear in the number of parameters. We demonstrate by a simulation of the transverse-field Ising model that our algorithm achieves a several orders of magnitude improvement in the number of measurements required for the same accuracy.