High-fidelity dimer excitations using quantum hardware

TL;DR

This paper demonstrates a resource-efficient quantum simulation method for capturing long-time dynamics of a quantum spin dimer, enabling comparison with neutron scattering experiments and advancing quantum hardware benchmarking.

Contribution

It introduces a direct, short-depth circuit approach called Resource-Efficient Fast-forwarding (REFF) for simulating long-time quantum dynamics on hardware.

Findings

Successfully simulated the triplet gap and splitting with high fidelity

Captured the dynamical structure factor comparable to experimental data

Showed feasibility of long-time quantum simulations on current hardware

Abstract

Many-body entangled quantum spin systems exhibit emergent phenomena such as topological quantum spin liquids with distinct excitation spectra accessed in inelastic neutron scattering (INS) experiments. Here we simulate the dynamics of a quantum spin dimer, the basic quantum unit of emergent many-body spin systems. While canonical Trotterization methods require deep circuits precluding long time-scale simulations, we demonstrate 'direct' Resource-Efficient Fast-forwarding (REFF) measurements with short-depth circuits that can be used to capture longer time dynamics on quantum hardware. The temporal evolution of the 2-spin correlation coefficients enabled the calculation of the dynamical structure factor $S(\mathbf{Q},\omega)$ - the key component of the neutron scattering cross-section. We simulate the triplet gap and the triplet splitting of the quantum dimer with sufficient fidelity to compare to experimental neutron data. Our results on current circuit hardware pave an important avenue to benchmark, or even predict, the outputs of the costly INS experiments.