Patent ID: 8854715

Claim:
A method comprising: inducing a surface state at a first input location; defining a propagation path for the surface state by imposing a first spatially-varying magnetic field having a first non-zero magnitude B 1 at a first magnetic field location r 1 on the propagation path and a second non-zero magnitude B 2 at a second magnetic field location r 2 on the propagation path, the first spatially-varying magnetic field being configured to produce a spatially-varying permittivity, the propagation path extending from the first input location to a first output location spatially separated from the first input location; and varying the propagation path by changing the first spatially-varying magnetic field to a second magnetic field having a third non-zero magnitude B 3 at the first magnetic field location r 1 and a fourth non-zero magnitude B 4 at the second magnetic field location r 2 , and wherein the ratio of B4/B3 is different from the ratio of B2/B1.