Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Abstract: K1.00135 : Observation of $\sigma _{x}$ coupling signal in a gap-tunable flux qubit
Author:
We experimentally demonstrate the \textit{in situ} tunability of
the gap of a
superconducting flux qubit, which was achieved by replacing the
smallest
Josephson junction of the qubit with a dc-SQUID. We observe
different gaps
as a function of the external magnetic pre-biasing field and the
local
magnetic field through the dc-SQUID controlled by high-bandwidth
on chip
control lines. The persistent current and gap behavior agree well
with the
numerical simulation results. We set the sensitivity of the gap
on the
control lines during the sample design stage. With a tuning range
of several
gigahertz on a qubit dynamics timescale, we observe coherent
system dynamics
at the degeneracy point [1]. We measured the microwave amplitude
dependence
of Rabi frequency at the same resonant frequency but at different
flux bias
of the gap-tunable flux qubit. It showed a systematical deviation
between
these two set of data, which indicated we observed $\sigma _{x}$
coupling
signal between the flux qubit and the microwave-line. Different from
conventional $\sigma _{z}$ coupling, this $\sigma _{x}$ coupling
has a
remarkable merit toward realization of idea QND measurement.
\\[4pt]
[1] Xiaobo Zhu, Alexander Kemp, Shiro Saito, and Kouichi Semba,
APPLIED
PHYSICS LETTERS 97, 102503 (2010).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.K1.135
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