Single photons and other quantum states of light are ideal carriers of quantum information due to their robust coherence properties. Quantum photonics indeed represents a convenient platform for implementing diverse protocols in quantum communications, quantum simulation, quantum computing or quantum metrology. To perform such protocols in experiments, quantum light states are manipulated by means of complex interferometers that transform and couple together multiple optical modes in a controlled way.

Interferometric devices present critical requirements in terms of interferometric stability and device compactness, which can be obtained by employing an approach based on integrated optics. In this scenario, direct writing of waveguide circuits by femtosecond laser micromachining is a powerful fabrication technology, incredibly versatile in realizing novel circuit designs and in condensing different photonic functionalities in a three-dimensional microstructured substrate.

Our research team was established as a synergy between researchers of the Physics Department of Politecnico di Milano and of the Institute of Photonics and Nanotechnologies of the National Research Council (IFN-CNR), and has been working in the field of integrated quantum photonics for more than fifteen years. The experiments are typically conceived in the framework of collaborations with renowned research groups in quantum optics and quantum information. For instance, joint research is ongoing with the Sapienza University of Rome, the University of Vienna in Austria, the International Iberian Nanotechnology Laboratory of Braga in Portugal.

In this thesis activity the student will contribute at the design, optimization and realization of advanced integrated-optics devices, exploiting the femtosecond laser micromachining technology, for applications in quantum information processing. The student will participate in ongoing research activities of the group; in particular, current areas of study include:

- universal photonic processors: reconfigurable devices capable of performing arbitrary linear operations on a set of optical modes;

- innovative optical modulators in glass;

- multi-mode waveguide devices for integrated manipulation of photonic qu-dits (the multi-level version of qu-bits);

- waveguide devices in doped crystals, for applications as solid-state quantum memories.

A thesis regarding one or more of these areas may be available, depending on the specific evolution of the research activities in a certain time. Feel free to contact Andrea Crespi or Roberto Osellame for further information.