State detection using coherent Raman repumping and two-color Raman transfers

Abstract

We demonstrate state detection based on coherent Raman repumping and a two-color Raman state transfer. The Raman coupling during detection selectively eliminates unwanted dark states in the fluorescence cycle without compromising the immunity of the desired dark state to off-resonant scattering. We demonstrate this technique using ${}^{137}{\mathit{Ba}}^{+}$ where a combination of Raman coupling and optical pumping leaves the metastable state, ${D}_{3/2}$ $|{F}^{\ensuremath{'}\ensuremath{'}}=3,{m}_{F}^{\ensuremath{'}\ensuremath{'}}=3\ensuremath{\rangle}$, optically dark and immune to off-resonant scattering. All other states are strongly coupled to the upper ${P}_{1/2}$ levels. We achieve a single-shot state-detection efficiency of $89.6(3)%$ in a 1-ms integration time, limited almost entirely by technical imperfections. Shelving to $|{F}^{\ensuremath{'}\ensuremath{'}}=3,{m}_{F}^{\ensuremath{'}\ensuremath{'}}=3\ensuremath{\rangle}$ before detection is performed via a two-color Raman transfer with a fidelity of $1.00(3)$.