Multiple-time Quantum Imaginary Time Evolution

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.

💡 Research Summary

This paper introduces a novel algorithm named Multiple-Time Quantum Imaginary Time Evolution (MT-QITE), which significantly advances the existing Quantum Imaginary Time Evolution (QITE) method for preparing ground states on quantum computers. While QITE is a powerful, deterministic, and ansatz-free algorithm, its practical application is hampered by a high measurement overhead and a strong dependence on the chosen Hamiltonian partition and local domain definitions.

The core innovation of MT-QITE lies in generalizing the single imaginary time step used in standard QITE to multiple independent time parameters. In the Trotter decomposition of the Hamiltonian, MT-QITE assigns a distinct time variable to each partition term (e.g., t1 for ĥ