Near-Optimal Chip-Based Photon Source Developed for Quantum Computing

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BRISTOL, England, Sept. 4, 2020 — Researchers at the University of Bristol have developed a new CMOS-compatible silicon photon source that satisfies all the requirements necessary for large-scale photonic quantum computing. To meet the stringent requirements for single-photon sources used in quantum computing, the researchers based their source on intermodal spontaneous four-wave mixing in a multimode silicon waveguide.

The intermodal approach to on-chip photon sources, where an interplay between multiple optical pump fields is used to generate photons, enables novel degrees of freedom to control the photon emission. By tailoring the geometry of a low-loss multimode waveguide and the on-chip temporal delay between the pump fields, the research team showed that the properties of the spontaneous photon emission could be engineered to achieve near-ideal photons.

To test their design, the researchers fabricated single-photon devices on standard silicon-on-insulator using CMOS-compatible lithography processes on a commercial wafer. Tests of the devices showed that the multimode waveguides significantly reduced transmission losses, enabling an intrinsic heralding efficiency of the source by approximately 90%. A high heralding efficiency is necessary to scale up quantum processing.

The researchers tested another feature essential for quantum computations — on-chip photon interference. Those experiments showed a raw data visibility of 96%, which the OSA reports is the highest so far in integrated photonics.

The achievement enables on-chip quantum operations between photons at an unprecedented level of precision, establishing the possibility to scale up low-noise photon processing in near-term quantum photonic devices.

According to the researchers, using a pump laser and increasing the uniformity of the fabrication process could improve the single-photon source.

The research will be presented at OSA Frontiers in Optics + Laser Science APS/DLS Sept. 14-17.

Published: September 2020
The term quantum refers to the fundamental unit or discrete amount of a physical quantity involved in interactions at the atomic and subatomic scales. It originates from quantum theory, a branch of physics that emerged in the early 20th century to explain phenomena observed on very small scales, where classical physics fails to provide accurate explanations. In the context of quantum theory, several key concepts are associated with the term quantum: Quantum mechanics: This is the branch of...
A waveguide is a physical structure or device that is designed to confine and guide electromagnetic waves, such as radio waves, microwaves, or light waves. It is commonly used in communication systems, radar systems, and other applications where the controlled transmission of electromagnetic waves is crucial. The basic function of a waveguide is to provide a path for the propagation of electromagnetic waves while minimizing the loss of energy. Waveguides come in various shapes and sizes, and...
Research & Technologyphotonic chipPhoton Sourcequantumquantum computationquantum computersWaveguidesiliconOSAOSA Frontiers in Optics + Laser Scienceon-chip

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