Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Abstract: K1.00138 : Observation of 0.2 ms Lifetime in a Cooper-pair Box
Author:
We have coupled a quasi-lumped element superconducting microwave
resonator with a resonant frequency of 5.44 GHz to an
Al/AlO$_{\mbox{x}}$/Al Cooper-pair box (CPB) charge qubit. The
resonator is in turn weakly coupled to a transmission line and
shows no higher resonant modes up to 20 GHz. By monitoring
perturbations of the resonant frequency, we have measured the
spectrum and lifetime ($T_{1}$) of the CPB at the charge
degeneracy point while the CPB was detuned from the resonator by
up to 3.5 GHz. The maximum $T_{1}$ of the CPB was 200 $\mu$s for
$f$ = 4 to 4.5 GHz, while $T_{1}$ decreased to 4 $\mu$s around 8
GHz. Our measured $T_{1}$'s imply that the loss tangent in the
AlO$_{\mbox{x}}$ junction barrier must be less than about
$4\times 10^{-8}$ at 4.5 GHz, about 4 orders of magnitude less
than reported in larger area Al/AlO$_{\mbox{x}}$/Al tunnel
junctions.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.K1.138
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