Kolthammer works on quantum photonics with an emphasis on nonclassical states of light and their applications to quantum information and sensing. Research highlights: (1) Gaussian Boson Sampling — first time-bin encoded GBS experiment using a loop-based interferometer with superconducting TES photon-number-resolving detectors, demonstrated enhancement in dense-subgraph search over classical methods (PRX 2022); (2) Squeezed state characterisation — nonclassicality certification using multiplexing layouts with superconducting TES detectors, sub-Poisson and sub-binomial statistics (PRA 2017); (3) Frequency-multiplexed photon pair sources — electro-optic frequency shifting for indistinguishable single-photon multiplexing without added multi-photon events; (4) Photonic quantum sensing — developing time-bin encoded platforms for quantum-enhanced sensing and quantum advantage demonstrations.