Nanotubes open new path toward quantum information technologies

September 7, 2015
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 information ranging from a credit card number to national security data is transmitted in streams of laser pulses. However, the information transmitted in this manner can be stolen by splitting out a few photons (the quantum of light) of the laser pulse. This type of eavesdropping could 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 to realization of such a communication scheme.

By demonstrating that incorporation of pristine into a silicon dioxide (SiO2) matrix could lead to creation of solitary oxygen dopant state capable of fluctuation-free, room-temperature single , Los Alamos researchers revealed a new path toward on-demand single photon generation. Nature Nanotechnology published their findings.

Photons emitted from lasers are distributed randomly in time. Therefore, "simultaneous" emission of two or more photons is possible. True single photon generation requires an isolated quantum mechanical two-level system that can emit only one photon in one excitation-emission cycle. Technological requirements of materials for quantum communication include the 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 that carbon nanotubes present technical challenges for use in quantum communications: 1) the materials were capable of single photon emission only at cryogenic temperature, and 2) their inefficient emission had strong fluctuations and degradation.

The Laboratory's new research has demonstrated that incorporation of pristine carbon nanotubes into a silicon dioxide (SiO2) matrix could lead to incorporation of solitary oxygen dopant states capable of fluctuation-free, room-temperature single photon emission in the 1100 - 1300 nm wavelength range.

The oxygen-doped nanotubes can be encapsulated in a SiO2 layer deposited on a silicon wafer. This presents an opportunity to apply well-established micro-electronic fabrication technologies for the development of electrically driven single photon sources and integration of these sources into quantum photonic devices and networks. Beyond implementation of 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 state-of-the-art photon detector, the team measured the temporal distribution of two successive photon emission events and demonstrated single photon emission. In addition, the team investigated the effects of temperature on photoluminescence emission efficiencies, fluctuations, and decay dynamics of the dopant states in the single-walled . The researchers determined the conditions most suitable for the observation of single-photon emission. 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, in which single photon emission is possible for only a few discrete wavelengths shorter than 1 µm.

Explore further: Quantum networks: Back and forth are not equal distances

More information: "Room-temperature single-photon generation from solitary dopants of carbon nanotubes." Nature Nanotechnology 10, 671–675 (2015) DOI: 10.1038/nnano.2015.136

Related Stories

Quantum networks: Back and forth are not equal distances

July 27, 2015

Quantum technology based on light (photons) has great potential for radically new information technology based on photonic circuits. Up to now, the photons in quantum photonic circuits have behaved in the same way whether ...

Hi-fi single photons

October 4, 2012

Many quantum technologies—such as cryptography, quantum computing and quantum networks—hinge on the use of single photons. While she was at the Kastler Brossel Laboratory (affiliated with the Pierre and Marie Curie University, ...

Recommended for you

Nano-decoy lures human influenza A virus to its doom

October 25, 2016

To infect its victims, influenza A heads for the lungs, where it latches onto sialic acid on the surface of cells. So researchers created the perfect decoy: A carefully constructed spherical nanoparticle coated in sialic ...

Nanofiber coating prevents infections of prosthetic joints

October 24, 2016

In a proof-of-concept study with mice, scientists at The Johns Hopkins University show that a novel coating they made with antibiotic-releasing nanofibers has the potential to better prevent at least some serious bacterial ...

New method increases energy density in lithium batteries

October 24, 2016

Yuan Yang, assistant professor of materials science and engineering at Columbia Engineering, has developed a new method to increase the energy density of lithium (Li-ion) batteries. He has built a trilayer structure that ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.