Controlled coupling of light and matter | Heiko Groß et al

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Artistic representation of a plasmonic nano-resonator realized by a narrow slit in a gold layer. Upon approaching the quantum dot (red) to the slit opening the coupling strength increases. Credit: Heiko Groß

March 6, 2018 (Phys.Org) -- Researchers from Würzburg and London have succeeded in controlling the coupling of light and matter at room temperature. They have published their results in Science Advances.

This achievement is particularly significant as it builds the foundations for the realization of practical photonic quantum technologies. While many demonstrations of optical quantum processes require cryogenic temperatures to protect the quantum states, the present work elevates the quantum processes to room temperature and introduces controllability, which could contribute to the development of quantum computers.

A light particle (photon) is generated when an excited molecule or a quantum dot returns to its low-energy ground state. This process is known as spontaneous emission, and is usually irreversible, i.e. an emitted photon will not simply return to the emitter to be absorbed again.

But if the emitter is intimately coupled to an optical resonator, the emitted photon remains in the vicinity of the emitter for a sufficiently long period of time, considerably boosting its chances of reabsorption. "Such a reversal of spontaneous emission is of high importance for quantum technologies and information processing, as it facilitates the exchange of quantum information between matter and light while preserving the quantum properties of both," says Professor Ortwin Hess of Imperial College.

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