I will present recent experimental work in which we have cooled calcium ions to near the ground state of motion by three varieties of Raman sideband cooling. We cooled the motion of single ions and pairs of ions in one dimension, obtaining mean vibrational quantum number n << 1. We studied a pulsed method and also two recently proposed continuous methods which I will describe.
I will also discuss experiments involving the joint spin and motional state of single ions and pairs of ions. We performed the `Schrodinger Cat' experiment in which a superposition of coherent states of motion of a single ion, entangled with the spin state, is prepared by resonantly driving the motion. The quantum superposition (as opposed to a mixture) is confirmed by observing an interference effect when the states are recombined. This technique can also be used to create a 2-ion quantum logic gate, entangling the internal states of a pair of ions. I will report on progress towards this important milestone in our laboratory.