What happened
- Researchers from Université Grenoble Alpes, CEA (with its IRIG and LETI institutes), Grenoble INP and the Laboratoire Charles Coulomb of the University of Montpellier and CNRS published on 28 October 2026 in Nature Communications a single-photon source made entirely of silicon.
- The source uses a W centre, a small defect in the silicon lattice, placed with nanometre precision inside a circular Bragg grating cavity, a structure that concentrates and steers light.
- It emits at 1,217 nanometres, in the near infrared, and reached a rate of 1.29 million detected photons per second at saturation.
- Under weak pulsed excitation, photons came out one at a time with 93% purity (plus or minus 2%).
Why it matters
- Light-based quantum technologies need sources that emit exactly one photon at a time. Most of those that work well use other materials, such as gallium arsenide, which have to be integrated with silicon chips.
- A source made of silicon can be built with the same processes the semiconductor industry already uses, making it easier to produce quantum photonic circuits at scale.
- The correlation measurement g(2)(0) = 0.06 shows that two photons are very rarely emitted together, which is what such a source is meant to achieve.
The number
1.29 million. That is how many photons per second the detector counted from the source at saturation, under continuous excitation.
Context
Colour centres in silicon, such as the W centre, have been studied for years as quantum emitters, but their light is weak and hard to collect. The cavity boosts emission in the zero-phonon line, the part of the light useful for quantum applications.
The authors observed that at saturation purity degrades because of repumping processes, and propose selective excitation schemes to fix it.
Integrated photonics is moving on several fronts Mamífero has covered: quantum dot photodiodes that match InGaAs in the infrared, a Japanese detector that counts photons by magnetic flux quanta and a silicon grating that revealed a hidden chirality in Smith-Purcell radiation. In computing, Quandela will deliver a photonic machine to Vietnam.
What’s next
- The next goal is photons that are indistinguishable from each other and emitted on demand, a requirement for quantum operations between several photons.
- The 1,217 nm wavelength is close to the telecom band, which could ease use of existing optical fibre.
- It remains to be shown that many of these sources can be made identical on the same wafer.
Bottom line
Silicon is the material industry knows how to make best, and until now it lacked a competitive single-photon source. The Grenoble and Montpellier work shows one with good purity and brightness. The pending step is to go from one source to hundreds of identical ones on the same chip.
Sources
- Lefaucher, B., Baron, Y., Jager, J.-B. et al., “Bright and pure single-photon source in silicon by nanoscale positioning of a color center in a microcavity”, Nature Communications, 28 October 2026, DOI 10.1038/s41467-026-78809-x
- Cover image: U.S. Department of Energy, public domain, via Wikimedia Commons
Edited by Rodrigo Cornejo. How we select and verify: who writes these notes.
