A quantum source of entangled photons built into a tiny chip has been developed

Researchers from Germany and the Netherlands have developed a quantum light source integrated into a chip.

The device generates entangled photons forquantum computing. The developers say that the new technology has made it possible to reduce the size of the source by more than 1,000 times, providing the necessary stability for scaling and mass production.

Engineers used "hybrid technology"which combined an indium phosphide laser, as well as a silicon nitride filter and resonator, into a chip. Two photons are created on the chip in a spontaneous nonlinear process from the laser field. Each of them covers a range of colors, with the colors of both photons being related to each other. In other words, photons are entangled and can store quantum information.

Now we can integrate the laser with othercomponents on a chip so that the entire quantum source is smaller than a one euro coin. Our tiny device could be considered a step towards the quantum advantage of the photon chip. Unlike Google, which currently uses ultracold qubits in cryogenic systems, a quantum advantage can be achieved with such photonic systems on a chip, even at room temperature.

Raktim Khaldar, study co-author

A quantum light source integrated into a coin-sized chip. Image: Institute of Photonics, Leibniz University of Hannover

Qubits (quantum bits, elementary unitsinformation in a quantum computer) are very sensitive to noise, the scientists explain. Until now, quantum light sources have required external and bulky laser systems, which has limited the possibilities for their use.

To implement a miniaturized device, the chip mustdriven by a completely noise-free laser field, which requires a built-in filter. Until now, researchers have not been able to find a material that would allow the integration of a laser, filter and resonator into a single chip, the developers say. Their hybrid technology solves this problem. In a series of experiments, they confirmed the high stability and efficiency of the finished device.

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On the cover: an artistic illustration of a quantum light source built into the chip. Image: Raktim Haldar, Michael Kues