  We report an experimental measurement of Landau-Zener transitions on an
individual flux qubit within a multi-qubit superconducting chip designed for
adiabatic quantum computation. The method used isolates a single qubit, tunes
its tunneling amplitude Delta into the limit where Delta is much less than both
the temperature T and the decoherence-induced energy level broadening, and
forces it to undergo a Landau-Zener transition. We find that the behavior of
the qubit agrees to a high degree of accuracy with theoretical predictions for
Landau-Zener transition probabilities for a double-well quantum system coupled
to 1/f magnetic flux noise.
