State Tomography of Capacitively Shunted Phase Qubits with High Fidelity
Matthias Steffen, M. Ansmann, R. McDermott, Nadav Y. Katz, Radoslaw C. Bialczak, Erik A. Lucero, M. Neeley, Eva Maria Weig, Andrew N. Cleland, John M. Martinis · Physical Review Letters · 2006
We introduce a new design concept for superconducting phase 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 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.