Recent experimental results in using ¹³⁷Ba in a miniaturized ion trap for quantum computation

Abstract

A suitable electronic level structure can be found in 137Ba+, which has a pair of hyperfine-split S1/2 ground states, allowing for storage of a `quantum bit' with weak parasitic coupling to the environment. Trapping and laser cooling of a single 137Ba+ ion was reported on a transition to the 2P1/2 level at a wavelength of 493 nm from a mixed isotopic Ba source with a natural abundance of 11% of 137Ba. Therefore, a cloud of ions was laser cooled on the 137Ba transition to keep the desired isotope in the center of the trap, whereas the other isotopes diffused out of the trap due to a destabilization with a dc trap bias. A readout of the qubit state pair in the S1/2 level was also performed using a shelving technique to the 4D3/2 level in a high-frequency trap.