Transcript Silicon Quantum Information Processing Mark Eriksson, UW-Madison, DMR 0325634

Silicon Quantum Information Processing
Mark Eriksson, UW-Madison, DMR 0325634
The fact that silicon is not a direct-band-gap
semiconductor presents certain opportunities and
challenges for quantum devices. To ensure welldefined spin qubits in silicon quantum dots, the
lowest orbital states, corresponding to the low
points or “valleys” in the strained silicon conduction
band, cannot have the same energy. This is
particularly challenging to ensure when devices are
grown on atomically rough substrates.
We have shown that the problem of roughness is
overcome in nanoscale devices, with spatial
dimensions approaching the roughness length
scale. The energy splitting between the low-lying
valley orbitals can be controlled using either the
gate voltages in a quantum point contact device, or
by applying magnetic fields. The results
demonstrate that there is no fundamental barrier to
quantum computing in silicon quantum dots due to
valleys.
Nature Physics 3, 41 (2007).
(a) A silicon quantum point contact device used to
measure valley splitting (only pairs of gates were
energized). (b) Conductance through the device
exhibits steps in units of e2/h, indicating a significant
splitting between all the energy levels, including both
valley and spin orbitals.
Silicon Quantum Information Processing
Mark Eriksson, UW-Madison, DMR 0325634
Outreach:
Our grant helps support the Physics
Learning Center at the University of
Wisconsin-Madison physics department,
both financially and through direct
involvement of our members. The
learning center trains undergraduates to
run small study groups as tutors/mentors
for introductory physics students, focusing
particularly on at-risk students, including
low-income and minorities. Contributions
from our ITR grant have allowed the
Learning Center to extend efforts to
calculus-based physics classes. This
year, two of our previous students have
become tutors, providing role models for
other students.
The Physics Learning Center works in
partnership with the NSF Louis Stokes
Wisconsin Alliance for Minority
Participation (WiscAMP) in science,
technology, engineering and mathematics.
PI Mark Eriksson (left) leads an informal lunch session of
undergraduate peer mentor tutors, and staff.
A Physics Learning Center staff member leads a review
session for calculus-based physics