Certain one-dimensional 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/l0) 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 three-dimensional p-wave 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).
- Pub Date:
- October 2001
- Condensed Matter - Mesoscale and Nanoscale Physics;
- Quantum Physics
- 16 pages, 5 figures, Latex and epsf, to be included in the proceedings of the Mesoscopic And Strongly Correlated Electron Systems conference (9-16 July 2000, Chernogolovka, Moscow Region, Russia), one reference added