We present a technique to completely characterise the spectral-temporal wave function of a broadband photon pair using spectral-shearing interferometry. Our method is fully self-referencing and is generalisable across a wide range of wavelengths. To demonstrate, we generate an entangled photon pair with controllable time-frequency entanglement and perform a full reconstruction. These results allow previously unobservable features of quantum states to be measured and utilised for the first time. We foresee this will unlock new opportunities in high-dimensional quantum technology, enabling the development of novel ways of generating and interacting with quantum systems.
@article{arxiv.1809.03727,
title = {Measuring the quantum state of a photon pair entangled in frequency and time},
author = {Alex O. C. Davis and Valerian Thiel and Brian J. Smith},
journal= {arXiv preprint arXiv:1809.03727},
year = {2018}
}