Berengut works on the atomic structure theory underpinning next-generation clocks: highly charged ions, whose optical transitions are both extremely narrow and exceptionally sensitive to variation of fundamental constants and to new physics, and the thorium-229 nuclear clock. He identifies which ionic species and transitions maximise sensitivity to the physics of interest while remaining experimentally accessible, and computes the many-body structure needed to interpret them — work that has directly guided the experimental HCI clock programmes at PTB, MPIK and NIST. Positioned against the established body of NV-ensemble quantum sensing work — DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity — clocks and magnetometers are the two great classes of quantum sensor; his work is on the frequency side of the same estimation problem that fixes pT/sqrt(Hz) performance on the magnetic side. Theory PI with close experimental collaborations.
Chantler's group is built around the idea that X-ray measurements can be made accurate, not just precise: the X-ray Extended Range Technique (XERT) delivers absolute absorption coefficients at the 0.02 per cent level, which in turn allows XAFS to be used for quantitative structure determination and allows high-accuracy tests of atomic theory. The second thread is precision X-ray spectroscopy of highly charged ions and exotic atoms as a test of bound-state QED, where discrepancies between theory and experiment remain unresolved. Positioned against the established body of NV-ensemble quantum sensing work — DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity — this is precision measurement at the other end of the electromagnetic spectrum: the methodological common ground with pT/sqrt(Hz) NV ensemble sensing is the obsessive treatment of systematics and absolute calibration that separates a sensitive measurement from an accurate one. Borderline inclusion, kept because the group's core competency is metrology rather than X-ray applications.
Indelicato performs high-precision X-ray spectroscopy of highly-charged and exotic (muonic, antiprotonic, pionic) atoms at large-scale facilities to test bound-state quantum electrodynamics in the strong-field regime, complementing LKB's hydrogen/molecular-ion precision-spectroscopy programmes.
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.