We sympathetically cool a trapped ${}^{112}{\mathrm{Cd}}^{+}$ ion by directly Doppler cooling a ${}^{114}{\mathrm{Cd}}^{+}$ ion in the same trap. This is the first demonstration of optically addressing a single trapped ion being sympathetically cooled by a different species ion. Notably, the experiment uses a single laser source, and does not require strong focusing. This paves the way toward reducing decoherence in an ion trap quantum computer based on ${\mathrm{Cd}}^{+}$ isotopes.

• Received 6 December 2001

DOI:https://doi.org/10.1103/PhysRevA.65.040304