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Status and recent progress of remote entanglement experiments with Barium-137 ions

Nathan Kurz, University of Washington

(Session 5 : Friday from 5:00-7:00)

Abstract. Because of its visible wavelength cooling transition, relatively high natural abundance, low-lying long-lived D states for shelving readout, and stable hyperfine qubit states spaced by 8.037 GHz, barium 137 represents an excellent ionic qubit candidate. We have built the necessary apparatus and developed techniques to trap and cool this ion. To date, we have demonstrated qubit initialization into the 6S1/2|F=1, mF=0> state by optical pumping, Rabi oscillations between 6S1/2|F=1, mF=0> and 6S1/2|F=2, mF=0> states, and the ability to state-selectively shelve the qubit to the 5D3/2 state for readout. Ultrafast pulses from a mode-locked Ti:Sapphire laser on resonance with the 6P3/2 transition have been shown to excite the ion with near unit probability on a sub-picosecond time scale. When tuned on resonance with the 6P1/2 transition, these pulses will entangle the spin state of the ion with the frequency of the emitted photonic qubit to be coupled into optical fiber and mode-matched on a beam splitter with the emitted photon of an identically prepared ion to generate a remote entangled ion pair. Long-term projects include the construction of a pulse programmer to drive the 8.037 GHz hyperfine transition with phase- and envelope-controlled pulses and construction of a thulium-doped fiber amplifier to increase optical power of the shelving laser at 1762 nm to improve readout speed.