Cold atoms, photons, and quantum correlations – QuaCor

Devices for quantum information computation and communication require the combined use of different quantum systems: photons can transmit informations over large distances, cold trapped atoms can be manipulated to enable quantum information processing, and atomic ensemble are suited for long-lived quantum memories, as well as non-linear generation of non-classical correlations. Cold atoms are a promising platform to manipulate light, and in this project we will focus on two specific quantum information tools: sources of correlated photons and memories, exploiting collective, multimode quantum states of atomic ensembles. We will address cooperative scattering in large atomic clouds to enhance these properties, i.e., we aim at showing how dipole-dipole interactions make it possible to tune both the lifetime and the optical coherences of the emitted light.
We will take advantage of the correlations between photons emitted in the spectrum of saturated atoms to show how multi-atom clouds can be a controllable source of correlated photons. Detecting correlations in a large quantum system can be a challenge, and the French and Brazilian teams will adopt different experimental setups to tackle this goal. The French team will also address the issue of memory in large dilute cloud, that manifests under the form of subradiant modes. The objective is to harness more efficiently the potential of these long-lived states, both in terms of coupling and of extraction of information. The Brazilian team will investigate experimentally the opposite regime of dense clouds, where mean-field optics breaks down due to the rise of correlations between the atomic dipoles. Finally, a theoretical objective is to determine how to achieve and detect quantum correlations between the atoms of large dilute clouds, through collective Rabi oscillations or synchronization.