http://physicsworld.com/cws/article/news/46375 Flipping spins, one proton at a time --- http://prl.aps.org/abstract/PRL/v106/i25/e253001 Phys. Rev. Lett. 106, 253001 (2011) [4 pages] Observation of Spin Flips with a Single Trapped Proton --- http://arxiv.org/abs/1104.1206 Observation of Spin Flips with a Single Trapped Proton (Submitted on 6 Apr 2011 (v1), last revised 3 May 2011 (this version, v2)) 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.