Hollenberg is the intellectual centre of gravity for diamond quantum sensing in Australia: a theorist-turned-programme-leader whose group develops NV-based quantum probes for biological systems and quantum-computing architectures in silicon and diamond. Current directions include the quantum-probe hyperspectral microscope, in which NV ensembles in a bulk diamond substrate report magnetic and spin-noise contrast from cells cultured directly on the surface; nanodiamond quantum probes for intracellular relaxometry and free-radical detection; theory of decoherence-based sensing (T1 relaxometry as a chemical-specificity channel rather than a nuisance); and single-cell magnetic resonance. He co-leads the Melbourne node of the ARC Centre of Excellence in Quantum Biotechnology (QUBIC) with Simpson and Hinde, which is explicitly chartered to build quantum sensors for live biology, including portable brain imagers. 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 — his programme is one of the small number worldwide that has carried those ensemble protocols all the way into cell culture and tissue rather than stopping at proof-of-principle magnetometry. Preferred attribute present: the group's emphasis is on sensitivity and biological specificity rather than device fabrication, and QUBIC funding runs to 2030 with recurring postdoc recruitment.