CEA-Irig was among the partners on a French national research agency (ANR) project that resulted in the on-demand emission of single photons in silicon at 1.28 µm, a wavelength used in telecommunications. They did it by introducing carefully-engineered defects into the material. The goal is to integrate this photon source into CEA-Leti chips for quantum communications.  

There is certainly no lack of research on point defects in silicon and, specifically, light-emitting defects formed by carbon pairs interacting with interstitial silicon atoms called G-centers. However, it had never been posited that these defects could emit single photons. The Octopus project implanted G-centers into the silicon and demonstrated that they could emit single photons. The findings were published in Nature Electronics.

A potential enabler of quantum communications

The G-center the researchers engineered turned out to be a very efficient source of photons that could potentially be embedded into chips. Using an external source to generate photons and then injecting them into the chip creates line losses. Single photons, however, are not affected by these reamplification issues.

The partners are now working with CEA-Leti to integrate the G-center into a chip to assess its potential for quantum communications. They are investigating the degree of spin freedom of isolated G-centers embedded in membranes of silicon 28, a spinless isotope. The G-center could be a future single-spin quantum memory, capable of storing the state of a single photon.