  Addressing subwavelength object and displacement is crucial in optical
nanometrology. We show in this Letter that nano antennas with subwavelength
structures can be addressed precisely by incident beams with singularity. This
accurate feeding beyond the diffraction limit can lead to dynamic control of
the unidirectional scattering in the far field. The combination of polarization
discontinuity of the incoming singular beam, along with the rapid phase
variation near the antenna leads to remarkable sensitivity of the far field
scattering to displacement at deep subwavelength scale. This opens a far field
deep subwavelength postion detection method based on the interaction of
singular optics with nano antennas.
