New light emitter for quantum circuits

New light emitter for quantum circuits A close-up look at the integrated chip that emits photons. (Image: courtesy of Ali Elshaari)

Researchers at KTH Royal Institute of Technology in Sweden developed integrated chips that can generate light particles on demand and without the need for extreme refrigeration.

In order for photons to deliver qubits on-demand in quantum systems, they need to be emitted in a deterministic, rather than probabilistic, fashion. This can be accomplished at extremely low temperatures in artificial atoms, but today the research group at KTH reported a way to make it work in optical integrated circuits—at room temperature.

The new method enables photon emitters to be precisely positioned in integrated optical circuits that resemble copper wires for electricity, except that they carry light instead.

The researchers harnessed the single-photon-emitting properties of hexagonal boron nitride (hBN), a layered material. hBN is a compound commonly used is used ceramics, alloys, resins, plastics and rubbers to give them self-lubricating properties. They integrated the material with silicon nitride waveguides to direct the emitted photons.

The researchers reported coupling of hBN single photon emitter to silicon nitride waveguides, and they developed a method to image the quantum emitters. Then in a hybrid approach, the team built the photonic circuits with respect to the quantum sources locations using a series of steps involving electron beam lithography and etching, while still preserving the high quality nature of the quantum light.

The achievement opens a path to hybrid integration, that is, incorporating atom-like single-photon emitters into photonic platforms that cannot emit light efficiently on demand.(

The paper has been published in Advanced Quantum Technologies.

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