Single Spin Detection by Magnetic Resonance Force Microscopy

Magnetic resonance force microscopy (MRFM) has been proposed as a method for greatly improving the sensitivity and spatial resolution of magnetic resonance imaging (MRI), perhaps even to the atomic level. It has also been proposed as a qubit readout device for spin-based quantum computers. While these challenging applications still remain distant goals, significant progress has been made.

We describe recent experiments at IBM that demonstrate that MRFM can detect individual subsurface electron spins associated with dangling bonds in silicon dioxide. The spin is manipulated by cantilever-driven cyclic adiabatic inversion and is detected via a slight frequency shift of an ultrasensitive micromachined cantilever. Spatial resolution of 25 nm in one dimension was obtained for spins located more than 100 nm below the magnetic tip of the cantilever. We will also discuss real-time feedback control of statistical fluctuations in small spin ensembles.