Tomography and Purification of the Temporal-Mode Structure of Quantum   Light
  High-dimensional quantum information processing promises capabilities beyond the current state of the art, but addressing individual information-carrying modes presents a significant experimental challenge. Here we demonstrate effective high-dimensional operations in the time-frequency domain of non-classical light. We generate heralded photons with tailored temporal-mode structures through ultrafast pulse shaping of a parametric downconversion pump. We then implement a quantum pulse gate, enabled by dispersion-engineered sum-frequency generation, to project onto programmable temporal modes, reconstructing the quantum state in seven dimensions. We also manipulate the time-frequency structure by selectively removing temporal modes, explicitly demonstrating the effectiveness of engineered nonlinear processes for mode-selective manipulation of quantum states. 
Vahid Ansari, John M. Donohue, Markus Allgaier, Linda Sansoni,   Benjamin Brecht, Jonathan Roslund, Nicolas Treps, Georg Har...
quant-ph