Observation of Spin Flips with a Single Trapped Proton
  Radio-frequency induced spin transitions of one individual proton are observed for the first time. The spin quantum jumps are detected via the continuous Stern-Gerlach effect, which is used in an experiment with a single proton stored in a cryogenic Penning trap. This is an important milestone towards a direct high-precision measurement of the magnetic moment of the proton and a new test of the matter-antimatter symmetry in the baryon sector. 
S. Ulmer (1,2 and 3), C.C. Rodegheri (1 and 2), K. Blaum (1 and 3), H.   Kracke (2 and 4), A. Mooser (2 and 4), W. Quint (3 ...
physics.atom-ph