Bright, near-IR photon emission from nanodiamonds is sharp enough for quantum communication
Bright, near-IR photon emission from nanodiamonds is sharp enough for quantum communication lead image
Single photon emitters (SPEs) are quickly becoming standard constituents of quantum optics devices. As a relatively new technology, however, quantum communication and encryption applications are still in need of viable emitters, especially for scalable applications. A report in APL Photonics describes a new kind of SPE that brightly emits in the near-IR with a narrow width in energy spread, a vital characteristic for generating indistinguishable photons for quantum communications.
Defects in diamond are fairly common sources of single photons, where nitrogen-vacancy (NV) centers are arguably the most popular version of the quantum emitters. The colors they can emit are determined by the zero-phonon lines (ZPLs) of the defects, where light energy from available optical transitions is not lost to lattice phonons. Only a few percent of photons from NV centers emit into these ZPLs.
Silicon-vacancy (SiV) centers are alternatives, with a ZPL towards the infrared at ∼738 nanometers, i.e., in a band compatible with high-quality optical microresonators. This work, however, reports on near-IR emitters with even longer wavelengths, while exhibiting sharp, sub-gigahertz linewidths. The emitters were formed in diamond nanocrystals, grown on sapphire substrates.
This narrow energy spread of the emitted photons is approximately five times that of its natural linewidth, as defined by the energy state’s lifetime. Such a narrow ZPL makes the emission viable for two-photon quantum interference, where linewidths that are too broad can’t provide sufficiently high probabilities for photon pairs to interfere and be indistinguishable.
The emitters’ exact origin is still in question and something the authors look to reveal through additional dopant experiments and theoretical simulations. “We hope to decode the atomic structure of this promising defect center in nanodiamonds,” said Toan Trong Tran, an author of the work.
Source: “Nanodiamonds with photostable, sub-gigahertz linewidths quantum emitters,” by Toan Trong Tran, Mehran Kianinia, Kerem Bray, Sejeong Kim, Zai-Quan Xu, Angus Gentle, Bernd Sontheimer, Carlo Bradac, and Igor Aharonovich, APL Photonics (2017). The article can be accessed at https://doi.org/10.1063/1.4998199 .
