Same-isotope cooling and FOFI qutrit in barium ions

The barium ion is an ideal species for scalable trapped-ion quantum computing because the wavelengths required for the control of the ion mostly lie in the visible wavelength range which is favorable for integrated optics technology. Also, the ion has metastable states with long lifetimes which is useful for omg-type operations. In this presentation, we discuss two novel techniques for controlling the barium ion. First, we discuss the use of light shift to realize a same-isotope cooling scheme that cools the collective motion of a ¹³⁸Ba⁺ ion chain. A tightly focused 532 nm beam will be used to induce a light shift, which spectrally differentiates the coolant ion from the data ion in a programmable manner. A global 1762 nm beam that is only resonant with the coolant ion will be used to drive a sideband-cooling cycle. We will then measure the impact of the cooling beam on the neighboring data qubit. Secondly, we show that there is a three-level system in the D_5/2 manifold of the ¹³⁷Ba⁺ ion where the two energy differences between the three quantum states become minimal at approximately the same magnitude of the bias magnetic field. Various options for controlling this first-order field-independent qutrit system is explored. The qutrit system can be used for efficient gate compiling.