Atom-light Quantum Interfaces

Efficient and controllable atom-light interactions are essential for numerous quantum applications, particularly for the high-fidelity transfer of quantum information. However, a fundamental challenge arises from the inherently weak coupling between a single atom and a photon in free space. This weak interaction leads to uncontrolled spontaneous photon emission, which in turn causes quantum information loss - a significant limitation in quantum optics and quantum information processing. Traditionally, dissipation is regarded as a source of errors, hindering quantum information and simulation tasks.

Traditional models of ultra-cold dilute atomic gases assume that atoms decay independently, in an uncorrelated fashion, leading to a linear (or sub-linear) efficiency scaling with atom density in quantum optics protocols. While such simplification is valid in dilute ensembles, it clearly overlooks wave interference and the fact that light scattering is a wave phenomenon. A new paradigm emerges when multiple atoms couple to the same radiation mode, as occurs in dense atomic media. In this regime, which is now at reach with state-of-the-art optical trapping techniques, light mediates effective (dipole-dipole) interactions between atoms, resulting in collective spontaneous emission effects, such as  superradiance (enhanced decay) and subradiance (suppressed decay).

This line of research focuses on exploiting cooperative photon scattering as a resource to enhance quantum protocols and to engineer non-trivial many-body quantum states of atoms and light.