1/f Flux noise in Josephson phase qubits.
We present a new method to measure 1/f noise in Josephson quantum bits (qubits) that yields low-frequency spectra below 1 Hz. A comparison of the noise taken at positive and negative bias of a phase qubit shows the dominant noise source to be flux noise and not junction critical-current noise, with a magnitude similar to that measured previously in other systems. Theoretical calculations show that the level of flux noise is not compatible with the standard model of noise from two-level state defects in the surface oxides of the films.
Bialczak
Radoslaw C
RC
Department of Physics, University of California, Santa Barbara, California 93106, USA.
McDermott
R
R
Ansmann
M
M
Hofheinz
M
M
Katz
N
N
Lucero
Erik
E
Neeley
Matthew
M
O'Connell
A D
AD
Wang
H
H
Cleland
A N
AN
Martinis
John M
JM