A solitary oxygen dopant (red sphere) covalently attached to the sidewall of the carbon nanotube (gray) can generate single photons (red) at room temperature when excited by laser pulses (green).
In optical communication, critical info eg credit card numbers to national security data needs to be secure. Eavesdropping can be prevented by encoding bits of information on quantum mechanical states (e.g. polarization state) of single photons. The ability to generate single photons on demand holds the key. Now, by incorporating single-walled carbon nanotubes, CNTs into a SiO2 matrix, it could lead to creation of solitary oxygen dopant state capable of fluctuation-free, room-temperature single photon emission, ie on-demand single photon generation.
Photons emitted from lasers are distributed randomly in time. Therefore, “simultaneous” emission of 2 or more photons is possible. True single photon generation requires an isolated quantum mechanical 2-level system that can emit only ` photon in one excitation-emission cycle.
~Tech requirements of materials for quantum communication include: ability to generate single photons in the 1,300 – 1,500 nanometer (nm) telecommunication wavelength range at room temperature and compatibility with silicon microfabrication technology to enable electrical stimulation and integration of other electronic and photonic network components.
~Earlier studies revealed CNT issues 1) the materials were capable of single photon emission only at cryogenic temperature, and 2) inefficient emission had strong fluctuations and degradation.
METHOD: The oxygen-doped nanotubes can be encapsulated in a SiO2 layer deposited on a silicon wafer.
APPS: Beyond quantum communication technologies, nanotube-based single photon sources could enable transformative quantum technologies including ultra-sensitive absorption measurements, sub-diffraction imaging, and linear quantum computing. The material has potential for photonic, plasmonic, optoelectronic, and quantum information science applications.
By using a photon detector, they measured the temporal distribution of 2 successive photon emission events and demonstrated single photon emission + investigated effects of temperature on photoluminescence emission efficiencies, fluctuations, and decay dynamics of the dopant states in the single-walled carbon nanotube. In principle, the emission could be tuned to 1500 nm via doping of smaller band-gap single-walled carbon nanotubes. This is a distinct advantage compared with some other materials, where single photon emission is possible for only a few discrete wavelengths https://www.lanl.gov/discover/news-stories-archive/2015/September/nanotubes-toward-quantum-info-technologies.php
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