Scattering theory in quantum optics, presented by Rahul Trivedi
Scattering matrices have been a key theoretical tool for the analysis of quantum field theories. Quantum optics studies the interaction of optical fields, which can be described by a field theory, with low dimensional systems (such as quantum emitters, optical cavities etc.) which can be described by a finite-dimensional or countably infinite-dimensional hilbert space. In this talk, I will go over the connection between the scattering matrices for Markovian quantum optical systems and the input-output formalism for time-dependent and time-independent quantum optical systems, and their computation. With the multi-emitter cavity QED system as an example, I will show how scattering matrices can allow development of a hierarchy of approximations calculable in polynomial time in the system size for simulating quantum optical systems, allowing analysis of large quantum optical systems. Finally, I will briefly mention possible applications of scattering matrices in understanding non Markovian quantum optical systems, as well as the interaction of low-dimensional quantum systems with structured 2D and 3D optical systems.
Nonlocal spin-exchange interactions in a near-concentric cavity, presented by Emily Davis
Photon-mediated interactions among atoms coupled to an optical cavity are a powerful tool for engineering quantum many-body Hamiltonians. We present direct observations of non-local spin-exchange ("flip-flop") interactions across hundreds of microns in a cloud of rubidium atoms strongly coupled to a single-mode optical cavity. Notably, the strength and sign of the interaction are optically tunable via controlling the power and detuning of a coherent drive field. Because we work within the F=1 spin-1 manifold, we also observe correlated m_F = +/-1 pair creation when initializing from m_F = 0. The optical access afforded by the near-concentric geometry enables imaging of the spatially-dependent dynamics inside the cavity with micron-scale resolution. I will also discuss prospects for generalizing to control the distance-dependence of the interactions.