Department of Physics, University of Basel, Switzerland
Meeting will be on zoom: Link to the colloquium
Many of the recent breakthroughs in quantum science and technology rely on engineering strong, controllable interactions between quantum systems. Typically, strong coupling is based on short-range forces or on placing the systems in high-quality electromagnetic resonators, restricting the range of the coupling to small distances. To overcome this restriction, we developed a light-mediated coupling scheme that enables long-distance Hamiltonian coupling [1,2]. In our experiment, we use a free-space laser beam to strongly couple a collective atomic spin and a micromechanical membrane over a distance of 1 meter in a room-temperature environment. The coupling is highly tunable and allows the observation of normal-mode splitting, coherent energy exchange oscillations, two-mode thermal noise squeezing and dissipative coupling. Our approach to engineer coherent long-distance interactions with light makes it possible to couple very different systems in a modular way, opening up a range of opportunities for quantum control and coherent feedback networks.
 T. M. Karg, B. Gouraud, P. Treutlein, K. Hammerer, Phys. Rev. A 99, 063829 (2019).
 T. M. Karg, B. Gouraud, C. T. Ngai, G.-L. Schmid, K. Hammerer, and P. Treutlein, Science 369, 174 (2020).