Formalism of rotating-wave approximation in high-spin system with quadrupole interaction

We investigate the rotating wave approximation applied in the high-spin quantum system driven by a linearly polarized alternating magnetic field in the presence of quadrupole interactions. The conventional way to apply the rotating wave approximation in a driven high-spin system 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 cannot be neglected for a multi-level quantum system. We propose the correct formalism to apply the rotating wave approximation in the full Hilbert space by taking this leakage into account. By estimating the operator fidelity of the time propagator, our formalism applied in the full Hilbert space unambiguously manifests great advantages over the conventional method applied in the reduced Hilbert space.

Automated summary

We investigate the application of rotating wave approximation in a high-spin quantum system driven by a linearly polarized alternating magnetic field in the presence of quadrupole interactions. The conventional method assumes dynamics restricted to the reduced Hilbert space, but leakage from the target resonance subspace becomes significant in a multi-level quantum system when the driving strength is strong or off resonant. We propose a correct formalism that considers this leakage and applies the rotating wave approximation in the full Hilbert space, showing great advantages over the conventional method.