Abstract: An apparatus for manipulating or modifying electromagnetic waves or electromagnetic waves or a beam of particles, eg atoms, ions, molecules or charged particles, the apparatus comprising a micro or nano electrical conductor crossbar network having multiple cross-over junctions that define respective scattering points for electromagnetic waves or the particles of the beam. At least one structural parameter of the crossbar network is selectively tuneable to obtain a desired manipulation or modification of said wave or beam when incident on the network in a pre-determined directional electrical conductor crossbar network (10) configured as an atomic beam diffraction grating. The direction of wave propagation of the atomic beam is indicated by the arrow (15).

Abstract: Apparatus for use in measuring and/or monitoring the relative position or displacement of two elements, includes a pair of elongate electrical conductors (10, 11) adapted to be associated with the respective elements, and means (12, 13, 18) for disposing the conductors at a mutual separation such that a detectable quantum tunnelling current may be generated between them on application of an electrical potential difference between the conductors.