Coherent Control of Macroscopic Quantum States in a Josephson Junction

Rabi oscillation between macroscopic quantum states of superconducting devices has important implications to the foundations of quantum mechanics as well as the development of quantum computing. At low temperature and low damping, a Josephson tunnel junction biased slightly below its critical current constitutes a macroscopic two-level quantum system. Here we report the results of a single-qubit rotation experiment in a NbN/AIN/NbN Josephson tunnel junction. We show that the state of the junction qubit can be controlled by varying the duration of the microwave pulses.