State tomography of capacitively shunted phase qubits with high fidelity

Matthias Steffen*, M. Ansmann, R. McDermott, N. Katz, Radoslaw C. Bialczak, Erik Lucero, Matthew Neeley, E. M. Weig, A. N. Cleland, John M. Martinis

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

172 Scopus citations


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.

Original languageAmerican English
Article number050502
JournalPhysical Review Letters
Issue number5
StatePublished - 2006
Externally publishedYes


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