Quantum Computation of Finite-Temperature Static and Dynamical Properties of Spin Systems Using Quantum Imaginary Time Evolution

TL;DR

This paper demonstrates the use of quantum imaginary time evolution (QITE) on near-term quantum hardware to compute finite-temperature properties of small spin systems, showcasing algorithmic improvements that enable practical calculations.

Contribution

The authors implement and optimize the QITE algorithm on IBM quantum devices to calculate finite-temperature properties of spin systems, highlighting new techniques for resource reduction and error mitigation.

Findings

Successfully computed finite-temperature observables for up to four-spin systems.

Implemented symmetry exploitation and circuit optimization to reduce quantum resources.

Achieved improved data quality through error mitigation techniques.

Abstract

Developing scalable quantum algorithms to study finite-temperature physics of quantum many-body systems has attracted considerable interest due to recent advancements in quantum hardware. However, such algorithms in their present form require resources that exceed the capabilities of current quantum computers except for a limited range of system sizes and observables. Here, we report calculations of finite-temperature properties including energies, static and dynamical correlation functions, and excitation spectra of spin Hamiltonians with up to four sites on five-qubit IBM Quantum devices. These calculations are performed using the quantum imaginary time evolution (QITE) algorithm and made possible by several algorithmic improvements, including a method to exploit symmetries that reduces the quantum resources required by QITE, circuit optimization procedures to reduce circuit depth, and error mitigation techniques to improve the quality of raw hardware data. Our work demonstrates that the ansatz-independent QITE algorithm is capable of computing diverse finite-temperature observables on near-term quantum devices.