The Kitaev honeycomb model has exact Z₂ gauge symmetry. Each plaquette has a conserved flux
Wp = ±1. Flipping a bond creates or annihilates visons in the two adjacent plaquettes.
Visons are Abelian anyons — braiding a fermion around a vison gives a phase of −1.
In the B-phase (all J equal), Majorana fermions become gapless; adding a magnetic field opens a gap
and makes the anyons non-Abelian (Ising anyons).