Mode-selection, purification, and ultrafast manipulation of quantum light with nonlinear waveguide devices
John Donohue, University of Paderborn
The temporal structure of quantum light offers an intrinsically high-dimensional and robust platform for encoding quantum information. In particular, the time-frequency degree of freedom can be explored in the frame of pulsed temporal modes, the ultrafast analogy to spatial Hermite-Gauss or orbital angular momentum modes. These overlapping temporal modes are naturally compatible with waveguide devices and fibre infrastructure, but present unique challenges to fully explore and exploit. In this talk, I will give an overview of the quantum pulse gate, a nonlinear operation which selectively upconverts individual temporal modes and their coherent superpositions, and present our experimental implementation using pulse shaping and dispersion-engineered PPLN waveguide devices. I will outline experimental demonstrations using the quantum pulse gate to manipulate the spectral shape of single photons, increase the efficiency of ultrafast measurement, tomographically reconstruct the temporal-mode structure of downconverted light, and verifiably select individual modes out of a mixed ensemble. I will also discuss how this device can be used for the reverse task, to prepare arbitrary superpositions of temporal modes, and how dispersion-engineered waveguide devices offer a platform for single-photon time-frequency state engineering.
This is joint work with, among others, Vahid Ansari, Markus Allgaier, Benjamin Brecht, and Christine Silberhorn.