Multiple-time Quantum Imaginary Time Evolution

TL;DR

The paper introduces MT-QITE, a parallelizable quantum algorithm that enhances ground state preparation efficiency and fidelity by using multiple imaginary time steps, reducing measurement costs and handling non-local Hamiltonians effectively.

Contribution

It presents the novel MT-QITE algorithm that improves upon existing QITE methods by using multiple imaginary times, increasing fidelity, reducing measurement overhead, and enabling parallelization.

Findings

MT-QITE improves ground state fidelity over traditional QITE.

The algorithm reduces measurement costs in quantum simulations.

Parallelization allows efficient handling of non-local Hamiltonians.

Abstract

Quantum Imaginary-Time Evolution (QITE) is a powerful method for preparing ground states on quantum hardware. However, executing QITE has costly measurement budgets for general Hamiltonians. Both fidelity and computational cost are strongly dependent on the definition of suitable local domains and Hamiltonian partitions. In this work, we introduce the Multiple-Time QITE algorithm (MT-QITE). We show how using more than one imaginary time substantially improves the fidelity of the resulting ground state as well as the measurement overhead with respect to the previously published QITE algorithm, while preserving its deterministic character and its independence from ad hoc ansatze. Moreover, unlike QITE and other QITE-based algorithms, MT-QITE is parallelizable, and we show that even in Hamiltonians with non-local interactions, partitioning may entail a computational advantage.