6. QUANTUM COMPUTING: Unpaired Majorana fermions in quantum wires
Abstract
Certain onedimensional Fermi systems have an energy gap in the bulk spectrum while boundary states are described by one Majorana operator per boundary point. A finite system of length L possesses two ground states with an energy difference proportional to exp(L/l_{0}) and different fermionic parities. Such systems can be used as qubits since they are intrinsically immune to decoherence. The property of a system to have boundary Majorana fermions is expressed as a condition on the bulk electron spectrum. The condition is satisfied in the presence of an arbitrary small energy gap induced by proximity of a threedimensional pwave superconductor, provided that the normal spectrum has an odd number of Fermi points in each half of the Brillouin zone (each spin component counts separately).
 Publication:

Physics Uspekhi
 Pub Date:
 October 2001
 DOI:
 10.1070/10637869/44/10S/S29
 arXiv:
 arXiv:condmat/0010440
 Bibcode:
 2001PhyU...44..131K
 Keywords:

 Condensed Matter  Mesoscale and Nanoscale Physics;
 Quantum Physics
 EPrint:
 16 pages, 5 figures, Latex and epsf, to be included in the proceedings of the Mesoscopic And Strongly Correlated Electron Systems conference (916 July 2000, Chernogolovka, Moscow Region, Russia), one reference added