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Topological Quantum Computing Made Practical?

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
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