Rabi oscillations, Ramsey fringes and spin echoes in an electrical   circuit
  We present a superconducting tunnel junction circuit which behaves as a controllable atom, and whose ground and first excited state form an effective spin 1/2. By applying microwave pulses, we have performed on this circuit experiments demonstrating the controlled manipulation of the spin : Rabi precession, Ramsey interferences, and spin echoes. 
D. Vion, A. Aassime, A. Cottet, P. Joyez, H. Pothier, C.Urbina, D.   Esteve and M.H. Devoret