Observation of separated dynamics of charge and spin in the Fermi-Hubbard model

TL;DR

This study demonstrates the digital quantum simulation of the one-dimensional Fermi-Hubbard model on a 16-qubit superconducting processor, revealing charge-spin separation in a highly excited regime beyond quasiparticle descriptions.

Contribution

It introduces a fast, accurate gate calibration and error mitigation techniques enabling faithful simulation of complex quantum dynamics on current noisy quantum hardware.

Findings

Observation of charge and spin density spreading velocity separation

Successful mitigation of systematic errors and decoherence effects

Simulation of over 600 two-qubit gates in a complex quantum circuit

Abstract

Strongly correlated quantum systems give rise to many exotic physical phenomena, including high-temperature superconductivity. Simulating these systems on quantum computers may avoid the prohibitively high computational cost incurred in classical approaches. However, systematic errors and decoherence effects presented in current quantum devices make it difficult to achieve this. Here, we simulate the dynamics of the one-dimensional Fermi-Hubbard model using 16 qubits on a digital superconducting quantum processor. We observe separations in the spreading velocities of charge and spin densities in the highly excited regime, a regime that is beyond the conventional quasiparticle picture. To minimize systematic errors, we introduce an accurate gate calibration procedure that is fast enough to capture temporal drifts of the gate parameters. We also employ a sequence of error-mitigation techniques to reduce decoherence effects and residual systematic errors. These procedures allow us to simulate the time evolution of the model faithfully despite having over 600 two-qubit gates in our circuits. Our experiment charts a path to practical quantum simulation of strongly correlated phenomena using available quantum devices.