Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - Q-PHOTONICS (Quantum fluids of photons in optically-induced structures)

Teaser

We are developing and studying systems that are able to realize “quantum nonlinear optics” – an optical regime, in which photons effectively interact and could manifest a quantum fluid. The strong photon-photon interactions are enabled by coherently coupling the photons...

Summary

We are developing and studying systems that are able to realize “quantum nonlinear optics” – an optical regime, in which photons effectively interact and could manifest a quantum fluid. The strong photon-photon interactions are enabled by coherently coupling the photons to strongly-interacting Rydberg states in an atomic ensemble, typically in the form of light-matter polaritons. Realizing and engineering quantum nonlinear optics is of high scientific and technological importance. From the fundamental side, it allows for studies of novel many-body physics, namely that of non-equilibrium (driven and dissipative) strongly-correlated systems. From the practical side, it enables photon-by-photon control for light manipulation and metrology, with applications in quantum computation, communication, and sensing.

Work performed

Our system of choice is a gas of either cold or hot atoms, excited by the propagating photons to high-lying Rydberg levels. The ERC project focuses on optically-driven spatial and spectral structures and on multimode operation, with an emphasis on counter-propagating photons. We have built two experimental setups – hot-atom and ultracold-atom systems – for realizing these ideas. We analysed the enhancement of a photonic quantum gates by an optically-induced cavity, that is, by a photonic resonator generated by illuminating the medium with a structured pattern. We showed that the circulation of photons back-and-fourth in the resonator enhances the gate fidelity, surpassing well-known limitations of such gates. Additionally, we demonstrated fast, coherent, excitation of electronic orbital, towards the realization of Rydberg-mediated nonlinear optics with hot atoms. For the same system, we developed and demonstrated a method to counteract the reduction of absorption due to thermal motion by using optical driving, which is crucial for reaching the quantum nonlinear optics regime with hot atoms. Finally, we develop a novel scheme for a robust two-photon phase gate based on counter-propagating polaritons.

Final results

We shall realize and study the new schemes we develop for Rydberg-mediated quantum nonlinear optics using optically-induced spatial and spectral structures, with cold and hot atoms.