We experimentally demonstrate the coherent oscillations of a tunable superconducting flux qubit by manipulating its energy potential with a nanosecond-long pulse of magnetic flux. The occupation probabilities of two persistent current states oscillate at a frequency ranging from 6 GHz to 21 GHz, tunable via the amplitude of the flux pulse. The demonstrated operation mode allows to realize quantum gates which take less than 100 ps time and are thus much faster compared to other superconducting qubits. An other advantage of this type of qubit is its insensitivity to both thermal and magnetic field fluctuations.
@article{arxiv.0809.1331,
title = {Coherent oscillations in a superconducting tunable flux qubit manipulated without microwaves},
author = {S. Poletto and F. Chiarello and M. G. Castellano and J. Lisenfeld and A. Lukashenko and C. Cosmelli and G. Torrioli and P. Carelli and A. V. Ustinov},
journal= {arXiv preprint arXiv:0809.1331},
year = {2009}
}