Speaker: Tomás Ramos
Affiliation: Institute for Theoretical Physics, University of Innsbruck and Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences
Date: Thursday, 16 June 2016 at 12:30
Location: Small Meeting Room, Serrano 121 (CFMAC)
Quantum optics studies the interaction between light and matter on the most fundamental level, namely, as energy exchanges between single photons and single quantum emitters. In the case of an excited atom interacting with the electromagnetic vacuum, this coupling is fundamentally isotropic, leading to a spontaneously emitted photon with no preferred direction. Nevertheless, recent advances in trapping atoms close to nanophotonic waveguides have shown that the strong confinement of light can naturally lead to situations in which excited atoms decay asymmetrically into left- and right-moving photons along the waveguide. This directional light-matter interaction has been recently called ‘chiral’, and opens
fascinating perspectives for realizing directional quantum networks with photons as quantum information carriers, as well as novel many-body quantum phases of light and matter.
In this context, we study the implications of chiral interactions on the driven-dissipative dynamics of many quantum emitters coupled via a one-dimensional waveguide. In particular, we determine how the interplay between coherent drive, chiral interactions and collective
decay can lead a chain of two-level atoms to a steady state that is pure and multi-partite entangled, which can be interpreted as a novel non-equilibrium magnetic phase of matter. In addition, we propose various purely atomic realizations of this model, where not only the emitters but also the waveguides are realized with atomic degrees of freedom such as Rydberg atoms, trapped ions, or Bose condensed atoms. Therefore, instead of photons, phonons or spin excitations mediate the chiral interactions, giving a high degree of control over the resulting open many-body dynamics for the emitters. These engineered
atomic setups also provide a route to controllably access physics beyond the Markovian quantum optics paradigm. For instance, using modern many-body numerical methods, we include the full dynamics of the atomic waveguide on the same footing as the emitters and thereby describe non-Markovian effects such as retardation in the exchange of excitations between emitters and non-linear dispersive effects. On the other hand, the same framework allows for the realization of `on-chip’ chiral quantum networks, which we illustrate with basic building blocks for quantum information applications, such as state transfer protocols or time-reversal of wave-packets.