Rotating wave approximation for quadrupole interaction with high spin

TL;DR

This paper investigates the rotating wave approximation in high-spin quadrupole systems, proposing full Hilbert space methods to account for leakage and counter-rotating effects, improving accuracy in strong or off-resonant driving regimes.

Contribution

It introduces a full Hilbert space approach for the rotating wave approximation in quadrupole interactions, addressing limitations of conventional methods under strong or off-resonant driving.

Findings

Full Hilbert space RWA improves fidelity estimates.

Counter-rotating hybridized RWA captures off-resonant effects.

Different RWA methods suit different experimental conditions.

Abstract

Rotating wave approximation in a quantum spin system driven by a linearly polarized alternating magnetic field with quadrupole interaction presents is investigated in detail in this paper. The conventional way to employ the rotating wave approximation is to assume the dynamics being restricted in the reduced Hilbert space. However, when the driving strength is relatively strong or the driving is off resonant, the leakage from the target resonance subspace along with the effects from the counter-rotating terms cannot be neglected anymore. We propose the rotating wave approximation applied in the full Hilbert space to take the leakage from the target resonance subspace into account. To include the effects from the counter-rotating terms, we utilize the counterrotating hybridized rotating wave method in the reduced Hilbert space. The performance of these rotating wave approximation methods is compared by estimating the state fidelity as well as the operator fidelity and the results reveal that different methods may be employed for different practical circumstances.