We observe at record-high speed the nonclassical nature of ultra-broadband biphotons, reducing the measurement time by four orders of magnitude compared to standard techniques of Hong-Ou-Mandel interference or sum-frequency generation. We measure the quantum wave-function of the broadband bi-photons, amplitude and phase, with a pairwise 'Mach-Zehnder' quantum interferometer, where bi-photons that are generated in one nonlinear crystal are enhanced (constructive interference) or diminished (destructive interference) in another crystal, depending on the bi-photon phase. We verify the quantum nature of the interference by observing the dependence of the fringe visibility on internal loss. Since destructive interference is equivalent to an attempt to annihilate in the second crystal (by up-conversion) the bi-photons that were created in the first crystal (by down-conversion), the fringe visibility is a measure of the quantum bi-photon purity of the broadband light. The measurement speed-up is due to the large homodyne-like gain from the strong pump (∼ − 10 7 9 ) in the upconversion efficiency of single bi-photons, which enables the use of simple photo-detection of the full, ultra-high photon flux instead of single-photon/ coincidence counting.Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. New J. Phys. 16 (2014) 053012 Y Shaked et al New J. Phys. 16 (2014) 053012 Y Shaked et al 1 Loss between the two crystals can be modeled as a BS, with reflection (absorption) and transmission amplitude coefficients r and t, positioned between the crystals, which mixes the New J. Phys. 16 (2014) 053012 Y Shaked et al

No abstract