Department of Physics
Condensed Matter Seminar

If one can be built, a quantum computer will be able to exploit the strange properties of quantum mechanics to perform qualitatively new kinds of computations -- most notably factoring large integers in polynomial time. Given the delicate nature of quantum states (one need only look at them to disturb them!) building a quantum computer will require some method to protect these states from the outside world, while at the same time allowing for their coherent manipulation. A particularly elegant proposal for doing this is called "topological quantum computation" (TQC). In TQC quantum information is stored in exotic states of matter which are intrinsically protected from decoherence, and quantum computation is carried out by dragging particle-like excitations (quasiparticles) around one another in two space dimensions. The resulting quasiparticle trajectories define world-lines in three dimensional space-time, and the corresponding computation depends only on the topology of the braids formed by these world-lines. In this talk I will review the basic ideas behind TQC, and describe our recent work showing how to find braids which can be used to perform arbitrary quantum computations using quasiparticles which are thought to exist in a recently observed fractional quantum Hall state.