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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
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Abstract

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.

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Matthias Steffen, M. Ansmann, R. McDermott, N. Katz, Radoslaw C. Bialczak, Erik Lucero, Matthew Neeley, E. M. Weig, A. N. Cleland, John M. Martinis. 2006-02-17. State tomography of capacitively shunted phase qubits with high fidelity. https://doi.org/10.1103/physrevlett.97.050502

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