Quantum Optics

Integrated quantum photonics combines high-density and high-performance functions on small footprint chips. In recent years, particular interest has been sparked by the possibility of exploiting the optical nonlinearities of silicon chips to generate multimode quantum states using frequency/time-like degrees of freedom. Our group has recently introduced the Bloch-Messiah analytical decomposition [Phys. Rev. Lett 125, 103601 (2020)] as a theoretical tool to decouple the complex dynamics of micro-resonators in terms of statistically independent observables that we have called morphing supermodes and to characterize their quantum properties. By applying this approach to light generated by a microresonator pumped in synchronous mode by a periodic train of pulses, we discovered [Phys. Rev. Research 5, 023178 (2023)] that traditional characterisation based on homodyne detection is incomplete because some quantum correlations (such as squeezing) remain hidden to this type of measurement. We have also studied classical solutions above threshold in CW pumping regimes and have characterized their quantum properties [Phys. Lett. A 493, 129272 (2024)]. On the other hand, ultrafast light pulses allow for studying system dynamics at ultrashort timescales and feature broad frequency comb structures used in high precision metrology. The field of ultrafast optics with coherent control techniques has flourished recently, leading to a rich toolbox for generating pulses with tailored temporal and spectral properties. Harnessing quantum features of light has driven progress in fundamental physics exploration, quantum communication, and quantum metrology. 

The QCUMbER (2015-2019) (H2020-FETOPEN-2014-2015-RIA #665148) project aimed to merge these fields to explore new capabilities from quantum light properties across extreme timescales and spectra. New measures for non-classicality in bosonic fields were derived (Phys. Rev. Lett. 122, 080402 (2019)), introducing a new class of single-mode optical states and determining the modal structure of non-degenerate parametric amplifiers. Collaborative work with partners from Laboratoire Kastler Brossel (LKB), Sorbonne Université, Paris was pivotal (Phys. Rev. Applied 15, 024016 (2021)). In the QuICHE project (2020-2024) (QuantERA, ANR-19-QUAN-0001) the group focuses on high-dimensional photonic quantum information, promising advantages over the qubit paradigm, including increased communication rates and robustness for entanglement distribution. It aims to enhance secure communication, improve quantum networks and metrology, and develop methods for dimension witnesses and entanglement certification. The project also introduces high-dimensional quantum temporal imaging, exploring possibilities for manipulating nonclassical states of light with temporal imaging systems. Recent research explores the conditions for making photons of different temporal shapes indistinguishable (Phys. Rev. A 107, 033705 (2023)), develops theories of time lenses and telescopes (Opt. Express 31, 38560 (2023)), and examines the modal structure and temporal resolution limits of imaging systems with finite temporal apertures (Phys. Rev. A 108, 043716 (2023)).