Near-surface quantum sensing

Abstract

We consider a magnetic dipole near a planar conducting surface as a probe for sensing an external magnetic field. We analyze the Quantum Fisher Information (QFI) for estimating the magnetic field amplitude. We consider three specific settings for the magnetic dipole: (i) in free space; (ii) oriented parallel to a planar surface, and (iii) oriented perpendicular to the surface. We demonstrate that the QFI is enhanced when the magnetic dipole is perpendicular to the surface, relative to other scenarios.