The First Integrated Photon Source to Deliver Large-Scale Quantum Photonics

May 29, 2020 by Luke James

Physicists from the University of Bristol in the UK have developed the world’s first integrated photon source with the potential to deliver large-scale quantum photonics.

The development of quantum technologies holds great promise across science, engineering, electronics, and indeed wider society on the whole. When quantum computers are developed and deployed at scale, they will be able to quickly solve problems that even the most powerful supercomputers of today struggle with, and this, in theory, will lead to many promising, revolutionary applications like the development of new materials. 

Now, a team of physicists at the University of Bristol are said to have developed an integrated photon source. The researchers published their findings in Nature Communications on May 19 and claim that their work is a “quantum leap” that represents a major step toward at-scale quantum technologies.


Generating and Controlling Photons

The reason that this development is so promising is that integrated quantum photonics as a platform could be used to develop quantum technologies. This is due to the platform’s capacity to generate and control photons in complex optical circuits, and leveraging the CMOS silicon industry for the fabrication of integrated devices could bring us circuits with thousands of optical fibers and components on a single millimeter-scale chip. 

However, a major challenge has limited the scaling of integrated quantum photonics—the lack of on-chip sources available to generate high-quality photons. Without this, errors in quantum computing processes quickly accumulate with more complex circuits and this leads to unreliable computations. 


A silicon photonic chip used to generate photons.

The silicon photonic chip used by Bristol researchers to generate and interfere photons. Image credited to S Paesani

Fabricated Using CMOS-Compatible Processes

Working with colleagues at the University of Trento in Italy, the Bristol researchers benchmarked the use of on-chip sources for photonics in quantum computing via a Hong-Ou-Mandel experiment, a core component of optical quantum information processing.

This experiment, the researchers claim, exhibited 96% visibility, the highest quality on-chip photonic quantum interference ever. The silicon photonic device was fabricated via CMOS-compatible processes in a commercial foundry, meaning that thousands of sources can be integrated on a single device. 

The research may represent a major step toward building quantum circuits at scale, bringing forth the potential development of several novel applications. "We have solved a critical set of noises that had previously limited the scaling of photonic quantum information processing,” said Dr. Stefano Paesani, the research paper’s lead author.

For example, hundreds of these sources could be used to build near-term noisy intermediate-scale (NISQ) photonic machines, where multiple photons can be processed to solve specialized tasks. 

Now that the researchers know how to build near-perfect photon sources, the team will scale the silicon platform to integrate tens to hundreds of them on a single chip. Circuits at this scale could make possible the solving of industrially relevant problems beyond the capability of present-day supercomputers.