Spatial confinement of atomic excitation by composite pulses in a doped solid

We experimentally demonstrate spatial confinement of atomic excitation by narrow-band composite pulse (NCP) sequences in a rare-earth ion-doped ${\text{Pr}}^{3+}\text{:}{\text{Y}}_2{\text{SiO}}_5$ crystal. The experimental data confirm that NCP sequences localize excitation far below the diameter of the driving laser pulse, with potential to proceed below the diffraction limit. We reach significant improvement of the spatial confinement compared to previous implementations. To this end, we derive several new classes of composite pulses that significantly outperform previously known sequences for the objectives of this study. In particular, the new NCP sequences are applicable also in inhomogeneously broadened ensembles, where most conventional composite pulse sequences fail. We systematically investigate the performance of the different classes of sequences and compare the results with numerical simulations, which agree very well with our experimental data. The findings serve as a step towards novel applications of composite pulse sequences to precisely prepare and manipulate excitation patterns in space, e.g., in quantum technology to address qubits with large spatial resolution.