Breakthrough for room temperature optical quantum computing

May 12, 2021 // By Nick Flaherty
Breakthrough for room temperature quantum photonics
Researchers at the KTH Royal Institute of Technology in Sweden have developed a technique to integrate quantum computing with optical fibre networks at room temperature.

"The quantum photonics approach offers a natural link between communication and computation," said Val Zwiller, Professor at KTH. "That's important, since the end goal is to transmit the processed quantum information using light."

However, to deliver qubits on-demand in quantum computing systems, photons need to be emitted in a deterministic, rather than probabilistic, fashion. This can be accomplished at extremely low temperatures in artificial atoms, but the team at KTH has developed a way to make it work in optical integrated circuits at room temperature.

The method enables photon emitters to be precisely positioned in integrated optical circuits using hexagonal boron nitride (hBN), a wide bandgap material. This is a layered material commonly used is used ceramics, alloys, resins, plastics and rubbers for its self-lubricating properties. This was integrated with silicon nitride waveguides to direct the emitted single photons.

This enables optical circuits with on-demand emission of photons at room temperature for quantum computing says Ali Elshaari, Associate Professor at KTH Royal Institute of Technology.

"In existing optical circuits operating at room temperature, you never know when the single photon is generated unless you do a heralding measurement," said Elshaari. "We realized a deterministic process that precisely positions light-particles emitters operating at room temperature in an integrated photonic circuit."

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 of single-photon emitters into photonic platforms that cannot emit light efficiently on demand.

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