Dressed-State Spectroscopy of Proton Spins in Water Beyond the Rotating-Wave Approximation

TL;DR

This paper reports the first experimental observation of dressed states of proton spins in water using a strong magnetic dressing field, confirming quantum Rabi model predictions beyond the rotating-wave approximation.

Contribution

It demonstrates the extension of dressed-state spectroscopy to proton spins in water, validating quantum Rabi model predictions in a new NMR context.

Findings

Observation of multiple spin-state transitions involving dressing-field quanta

Excellent agreement between measured spectra and theoretical quantum Rabi model

Extension of dressed-state spectroscopy to proton spins in water

Abstract

The quantum Rabi model provides the framework for describing a two-level system interacting with a strong oscillating field beyond the rotating-wave approximation. We report the first experimental observation of the resulting dressed states of proton spins in water, realized using a Rabi-type setup with a strong off-resonant magnetic dressing field. The measured resonance spectrum exhibits multiple spin-state transitions involving several dressing-field quanta, including higher-order resonances predicted by the quantum Rabi model. The dressed-state energies show excellent agreement with theoretical expectations, extending dressed-state spectroscopy to proton spins and opening new possibilities for precision spin manipulation in nuclear magnetic resonance and related precision measurements.