Manipulating the Quantum State of an Electrical Circuit
D. Vion, A. Aassime, Audrey Cottet, P. Joyez, H. Pothier, C. Urbina, Daniel Esteve, Michel Devoret · Science · 2002
We have designed and operated a superconducting tunnel junction circuit that behaves as a two-level atom: the "quantronium." An arbitrary evolution of its quantum state can be programmed with a series of microwave pulses, and a projective measurement of the state can be performed by a pulsed readout subcircuit. The measured quality factor of quantum coherence Qphi approximately 25,000 is sufficiently high that a solid-state quantum processor based on this type of circuit can be envisioned.