Microresonator Delivers Photon Pairs At Record Efficiency

Researchers in the United States created a lithium-niobate microresonator on a chip. They demonstrated that it could generate photon pairs more than 100 times faster than other chip-based photon sources. They believe that by combining it with other optical components, the tiny resonator could aid in the “widespread adoption” of quantum devices.

The spontaneous parametric down-conversion nonlinear process generates photon pairs in the microresonator, built on a micron-thin layer of crystal (SPDC). A powerful laser beam directed at the device confines photons within the structure, where some split into pairs of photons with lower energies.

One of the most commonly used crystals for such research is lithium niobate, an artificial salt that exhibits significant optical nonlinearities; it is transparent across a wide frequency range and generates strong electro-optic effects. As a result, the material is already used in a wide range of optical and electronic devices.

However, integrated lithium niobate as a thin film on top of an insulator has yet to make fully practical quantum devices possible. Such devices must meet several stringent requirements before functioning as bright, pure sources of quantum particles. They must exhibit strong nonlinearities, tightly confine light over long periods, and ensure phase matching between incoming and outgoing light waves.

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