Research ArticleQuantum Physics

Light-mediated strong coupling between a mechanical oscillator and atomic spins 1 meter apart

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Science  10 Jul 2020:
Vol. 369, Issue 6500, pp. 174-179
DOI: 10.1126/science.abb0328

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Strongly coupled at distance

The development of hybrid quantum systems provides a flexibility that allows for various components to be coupled together, thereby expanding the opportunity to build quantum sensors and devices that can be designed for specific purposes. Key to doing so is being able to strongly couple the different components. Most developments to date have relied on the components being in close proximity, which can hamper design flexibility. Karg et al. used a laser to induce strong coupling between a cloud of atoms and an optomechanical membrane. With the components separated by 1 meter, this approach demonstrates a methodology of coupling quantum systems and easing up restrictions on spatial proximity.

Science, this issue p. 174


Engineering strong interactions between quantum systems is essential for many phenomena of quantum physics and technology. Typically, strong coupling relies on short-range forces or on placing the systems in high-quality electromagnetic resonators, which restricts the range of the coupling to small distances. We used 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 engineering 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.

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