State tomography of capacitively shunted phase qubits with high fidelity.
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.
Steffen
Matthias
M
Department of Physics and California Nanosystems Institute, University of California, Santa Barbara, CA 93106, USA.
Ansmann
M
M
McDermott
R
R
Katz
N
N
Bialczak
Radoslaw C
RC
Lucero
Erik
E
Neeley
Matthew
M
Weig
E M
EM
Cleland
A N
AN
Martinis
John M
JM