We introduce a new design concept for superconducting quantum bits (qubits) in which we explicitly separate the capacitive element from the Josephson tunnel junction for improved qubit performance. The number of two-level systems (TLS) that couple to the qubit is thereby reduced by an order of magnitude and the measurement fidelity improves to 90%. This improved design enables the first demonstration of quantum state tomography with superconducting qubits using single shot measurements.
@article{arxiv.cond-mat/0602432,
title = {State tomography of capacitively shunted phase qubits with high fidelity},
author = {Matthias Steffen and M. Ansmann and R. McDermott and N. Katz and Radoslaw C. Bialczak and Erik Lucero and Matthew Neeley and E. M. Weig and A. N. Cleland and John M. Martinis},
journal= {arXiv preprint arXiv:cond-mat/0602432},
year = {2009}
}