Temporal-mode tomography of single photons

Accessing a high dimensional Hilbert space spanned by temporal modes (TMs) of single-photons is an intriguing idea for quantum information protocols, though it is experimentally challenging. The quantum pulse gate (QPG), a group-velocity matched sum-frequency process, can perform arbitrary TM resolved measurement. We present a thorough characterisation of measurement operators of a QPG and we show that this device is capable of performing full state tomography with 99% fidelity. Moreover, we use this device for TM tomography of pure and mixed heralded single-photon states in 7-dimensional Hilbert space.