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 ${}^{137}{\mathrm{Ba}}^{+}$ where a combination of Raman coupling and optical pumping leaves the $D_{3/2}$ $|F"=3,m_F"=3⟩$ metastable state 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 $1\mathrm{ms}$ integration time, limited almost entirely by technical imperfections. Shelving to the $|F"=3,m_F"=3⟩$ state before detection is performed via a two-color Raman transfer with a fidelity of $1.00(3)$.