AbstractBy their very nature, ultrafast quantum states lend themselves well to being expressed in terms of a broadband mode basis, a complete set of orthogonal superpositions of monochromatic frequency modes. The promise of pulsed quantum optical systems at ultra-high repetition rates, as well as the possibility to use broadband modes as a carriers of quantum information is fueling the emergence of ultrafast quantum light sources. We have implemented an exceptionally bright parametric downconversion source of indistinguishable photons (ca 3*10^7/s/mW) in a single mode KTP waveguide with the help of spectral engineering. We explore the spectral properties of our source in terms of broadband modes. Finally we apply spectral engineering to a frequency upconversion process, to create an ultrafast photon switch sensitive on broadband modes.
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