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.

Quiney (currently Head of School) is a theorist of coherent imaging and relativistic atomic structure. His signature contribution is the theory of X-ray free-electron-laser imaging of single particles, including the modelling of radiation damage and ionisation dynamics during the pulse — the question of whether you can extract structure faster than you destroy it — plus phase-retrieval algorithms for coherent diffractive imaging and ptychography. He also works on relativistic quantum chemistry and atomic structure. 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 — the connection is methodological rather than physical: his group develops the inverse-problem and photon-budget theory that governs how much information can be pulled out of a shot-noise-limited measurement, which is the same limit that fixes pT/sqrt(Hz) performance in NV ensembles. Theory-first PI with strong coupling to experimental synchrotron/XFEL programmes.