$^{138}$Ba$^{+}$ Ion-Photon Entanglement using Ultrafast Pulses

We present preliminary evidence of entanglement between the ground state of a trapped $^{138}$Ba$^{+}$ ion and the polarization state of the photons it spontaneously emits. The spontaneously emitted photons result from weak excitation by short ($\sim$40 ns) pulses of resonant CW laser light of the ions initially prepared in a single Zeeman ground state. This protocol is facilitated by the presence near the trap of an integrated electrode that allows ground state spin flips to be driven in under a microsecond. We also present our work toward improved entanglement fidelity by employing ultrafast pulses from a mode-locked Ti:Sapphire laser for ion excitation, with the ultimate goal of doing remote entanglement of barium ions in distant traps. Barium is a particularly good candidate for such research due to the relatively long wavelength of the transitions involved, which makes it suitable for fiber optic transmission over long distances.