At the most fundamental level, light-matter interaction can be described by the interaction between single photons and single quantum emitters which underlies most optical phenomena and applications. Light-matter quantum interfaces that control and employ this interaction are the basis for game-changing new technologies such as quantum computers, quantum communication, or quantum simulation applications.
In this project, we will realize a new experimental platform that provides a highly efficient and fully fiber-integrated light-matter quantum interface. The platform is based on a new type of optical resonator: a fiber-ring-resonator that includes a tapered section with a sub-micron diameter waist for efficiently interfacing atoms with the evanescent part of the guided light. Thanks to the inherent fiber-integration, key resonator properties, such as free-spectral range or optical finesse, can be freely adjusted. This renders the proposed platform a highly flexible toolbox for a broad range of fundamental experiments as well as for future quantum optical applications.
Within the project, we will interface the resonator with ensembles of laser-cooled atoms which enables us to reach extremely large collective light-matter coupling strengths. Making use of the inherent fiber-integration, we can adjust the length of the resonator in a straightforward way which allows us to realize resonator lengths reaching up to 100 m. Remarkably, this does not affect the cooperativity of the atom-resonator system and thus opens up the way to study so far unexplored regimes of light-matter interaction such as the multimode strong coupling regime. There, the collective atom-light coupling rate even exceeds the free-spectral range of the resonator, and the atoms simultaneously strongly interact with many longitudinal resonator modes. In addition, the resonator can be adjusted such that it provides a chiral, i.e. direction-dependent, light-matter interaction – a recently discovered new paradigm of quantum optics. In this regime, the standard models of collective light-matter coupling do not apply and, making use of the advantageous properties of the resonator platform, we will experimentally study in detail how collective phenomena such as sub- and superradiance change in this novel regime.
Another key goal is to demonstrate that the proposed system constitutes a novel experimental platform for advanced quantum simulation and computation protocols. For this purpose, the resonator will be integrated on an atom-chip setup which acts as a source for ultra-cold atoms. In the combined system, the resonator photons then mediate a long-range interaction between the atoms which we will use to implement quantum algorithms based on quantum annealing. Together with the capability of exploring and investigating qualitatively new regimes of light-matter coupling, this will pave the way towards establishing this hybrid system as a key resource for future quantum-enabled photonic technologies as well as a for fundamental research on quantum physics and quantum optics.
