APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014;
Denver, Colorado
Session T36: Focus Session: Semiconductor Qubits: Magnetic Control & Nuclear Dynamics
11:15 AM–2:15 PM,
Thursday, March 6, 2014
Room: 703
Sponsoring
Unit:
GQI
Chair: Jason Petta, Princeton University
Abstract ID: BAPS.2014.MAR.T36.4
Abstract: T36.00004 : Control and coherence of Loss-DiVincenzo qubits in Si/SiGe quantum dots
11:51 AM–12:27 PM
Preview Abstract
Abstract
Author:
Pasquale Scarlino
(Kavli Institute of Nanoscience, TU Delft)
Electron spins in Si/SiGe quantum dots are one of the most promising
candidates for a quantum~bit~for their potential to scale up and their long
dephasing time. We report for the first time the experimental realization of
single electron spin rotations in a single quantum dot (QD) defined in a
Si/SiGe 2D electron gas. The electron spin is read out in single-shot mode
by a QD charge sensor. Spin rotations are achieved by applying microwave
excitation to one of the gates, which oscillates the electron wave function
back and forth in the gradient field produced by cobalt micro-magnets
fabricated near the dot. By measuring the electron spin resonance frequency
as a function of the external magnetic field, the electron g-factor of 1.994 $\pm$ 0.007 is determined. A dephasing time of T2*$=$850 ns, about 20
times longer than that in GaAs quantum dots, is extracted from the linewidth
of the electron spin resonance peak. We observe spin Rabi oscillations with
Rabi frequencies up to 5 MHz. Because the coherence time can be longer than
the spin manipulation time, we are able to rotate the electron spin even
when detuned in frequency, giving the typical chevron pattern when sweeping
detuning and microwave burst time. We also realized Ramsey interference
experiments, giving a free induction decay T2* $=$ 800 ns. Looking closely,
all these data exhibit interference patterns resulting from the contribution
of two resonances separated by a frequency difference $\Delta $f $=$2-4 MHz.
We tentatively interpret these two resonances as intra-valley spin resonance
for two different valley states. Due to the valley-orbit mixing, the orbital
wavefunction of each valley state is slightly different, which yields a
different Zeeman splitting for each valley state. Finally, we perform
Hahn-echo measurement and deduce, for the first time in Si/SiGe, a single
spin T2$=$37$\mu $s.\\[4pt]
This work has been done in collaboration with E. Kawakami, Kavli Institute of Nanoscience, TU Delft, Lorentzweg 1, 2628 CJ Delft, The Netherlands; D. Ward, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA; F.R. Braakman, Kavli Institute of Nanoscience, TU Delft; D. E. Savage, M. G. Lagally, S.N. Coppersmith, M. A. Eriksson, University of Wisconsin-Madison; and L. M. K. Vandersypen, Kavli Institute of Nanoscience, TU Delft.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.MAR.T36.4