Telecom and Rubidium Resonant Single Photons from a Barium Ion Via Quantum Frequency Conversion

Trapped ions typically emit short wavelength photons with limited propagation range due to substantial attenuation in optical fibers. To extend the transmission range of photons from trapped Ba$^{\mathrm{+}}$ ions, quantum frequency conversion (QFC) in a nonlinear crystal allows for translation of the ion's native wavelength to a more desirable wavelength. The conversion is performed in a periodically poled lithium niobate waveguide via difference frequency generation between the ion's photon and a high intensity pump. Ba$^{\mathrm{+}}$ has two strong optical dipole transitions which produce visible photons at 650 nm and 493 nm. Here, we show single stage conversion of 650 nm Ba$^{\mathrm{+}}$ resonant laser light to the telecom O-Band (1259 nm). We also show single stage conversion of single 493 nm photons from a $^{\mathrm{138}}$Ba$^{\mathrm{+}}$ ion to 780 nm and, via measurement with a wavemeter, confirm its resonance with $^{\mathrm{87}}$Rb [1]. Finally, we show two-stage conversion of single 493 nm photons to the telecom C-Band near 1550 nm. We discuss the tunability and optimization of the conversion setup, as well as signal-to-noise at the single photon level. These results, as well as QFC results using Ca$^{\mathrm{+}}$ [2,3] provides a pathway for remote inter-ion quantum networking and possible hybrid networking. [1] J.D. Siverns, J. Hannegan, Q. Quraishi, arXiv:1801.01193 (2018) [2] T. Walker, et. al., arXiv:1711.09644 (2017) [3] M. Bock, et. al., arXiv:1710.04866 (2017)