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Condensed Matter Physics Seminar

Thursday, December 7, 2000, 2 p.m.

Plant Sciences Building, Room 1130
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*Unpaired Majorana fermions in quantum wires*

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Alexei Kitaev

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(Microsoft Research and Landau Institute for Theoretical Physics)

**Abstract:** Certain one-dimensional Fermi systems have an energy
gap in the bulk spectrum while the boundary states are described by one
Majorana operator per boundary point. As a result, a finite system
of length *L* posesses two ground states with different fermionic
parity whose energy difference is proportional to exp(-*L/a*).
We find a general condition on the bulk electron spectrum which determines
whether this situation is the case. The condition is satisfied in
the presense of arbitrary small energy gap induced by a 3-dimensional *p*-wave
superconductor, provided that the original spectrum has an odd number of
Fermi points in each half of the Brillouin zone (each spin component counts
separately!). Such systems can be used as qubits as they are intrinsically
immune to decoherence.
**Host:** Victor Yakovenko

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