Download Topological Insulators

Topological Quantum
Computing Made
Practical?
PHY0822671
Topological quantum computing
(TQC), in which the data are protected
against decoherence because they are
stored and manipulated as shapes, is
a highly desirable goal in quantum
information science. Unfortunately, the
only physical system in which anything
approaching topological protection has
been seen is a two-dimensional
particle gas experiencing the fractional
quantum Hall effect. That effect
requires formidable extremes of low
temperature and high magnetic field,
as well as rare, specially fabricated
materials, making experimental
exploration of.TQC very difficult.
But now a team supported by the JQI Physics Frontier Center has produced a theoretical design for a simple system that should
produce topologically protected units of quantum data. It does not require exotic materials or extremely cold temperatures, and
can be tested easily on the benchtop. A sheet of normal superconductor (such as niobium) with a hole in it is placed atop a layer
of ordinary semiconductor, and the superconductor induces a region of weak superconductivity in the semiconductor via the
“proximity effect.” As magnetic field lines penetrate this thin proximity region, they cause vortices to form. Each of those vortices
traps a single quantum state. Moving or “braiding” these states results in quantum information stored as topological patterns.
J.D. Sau, R.M Lutchyn, S. Tewari and S. Das Sarma, “Generic New
Platform for Topological Quantum Computation Using Semiconductor
Heterostructures, Phys. Rev. Lett. 104, 040502 (2010)