Pohl is the central figure in muonic-atom precision spectroscopy -- the measurements that produced the proton-radius puzzle. Replacing the electron with a muon shrinks the Bohr radius ~200x and amplifies sensitivity to nuclear structure by ~10^7, so laser and microwave spectroscopy of muonic hydrogen/deuterium/helium yields charge and magnetization radii at otherwise unreachable precision. Current pushes: the CREMA/HyperMu measurement of the proton's magnetic (Zemach) structure via the muonic-hydrogen hyperfine splitting, and QUARTET, targeting ~10x better charge radii for light nuclei from Li to Ne. Work is done at PSI with cryogenic targets, ultrafast trigger lasers and X-ray detector arrays. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), this is a different sensing regime entirely -- the 'sensor' is the atom and the challenge is systematics at the 10^-5 level -- but it is a strong pivot for a postdoc who wants extreme metrology and detector work rather than condensed-matter spin physics.