Barium isotope 137 has nuclear spin 3/2, which gives rise to hyperfine interaction and ground state splitting of about 8 GHz. Hyperfine states with there effectively infinite lifetime and long coherence are excellent candidates for quantum information storage and processing. We have developed a robust scheme for ¹³⁷Ba⁺ qubit preparation and detection.

While it is convenient to store quantum information in hyperfine states of trapped ions, sending this information over any distance longer than a perhaps millimeter is best done by using photons. We are studying coherent coupling between quantum states of the trapped ions and single photons.

Short, high-intensity laser pulses can be used to drive fast quantum logic gates between trapped ions. High degree of control over the pulses properties is necessary for high-fidelity gates. We are using picosecond and femtosecond modelocked lasers to drive single Ba ions and enable such gates.

We are developing high numerical aperture reflective optics to improve fluorescence collection efficency from the trapped ions. Our approach is to use spherical mirrors placed in vacuum in the vicinity of the ions, with aspheric correctors outside the vacuum to achieve a near diffraction-limited performance.

A single trapped Ba⁺ is an ideal quantum system that is nearly free of systematic perturbations. To exploit this we have developed a laser to coherently address resolved sublevels of the long-lived 5D_3/2 manifold. With this tool we are able to perform precision spectroscopy of single Barium ions to observe phenomena arising from atomic and nuclear physics.