We have observed coherent time evolution between two quantum states of a superconducting flux qubit comprising three Josephson junctions in a loop. The superposition of the two states carrying opposite macroscopic persistent currents is manipulated by resonant microwave pulses. Readout by means of switching-event measurement with an attached superconducting quantum interference device revealed quantum-state oscillations with high fidelity. Under strong microwave driving it was possible to induce hundreds of coherent oscillations. Pulsed operations on this first sample yielded a relaxation time of 900 nanoseconds and a free-induction dephasing time of 20 nanoseconds. These results are promising for future solid-state quantum computing.
@article{arxiv.cond-mat/0305461,
title = {Coherent Quantum Dynamics of a Superconducting Flux Qubit},
author = {I. Chiorescu and Y. Nakamura and C. J. P. M. Harmans and J. E. Mooij},
journal= {arXiv preprint arXiv:cond-mat/0305461},
year = {2009}
}
Comments
submitted 2 December 2002; accepted 4 February 2003