This little light of mine: Changing the color of single photons emitted by quantum dots

Two important resources for quantum information processing are the transmission of data encoded in the quantum state of a photon and its storage in long-lived internal states of systems like trapped atoms, ions or solid-state ensembles.

Ideally, one envisions devices that are good at both generating and storing photons. However, this is challenging in practice because while typical quantum memories are suited to absorbing and storing near-visible photons, transmission is best accomplished at near-infrared wavelengths where information loss in telecommunications optical fibers is low.

To satisfy these two conflicting requirements, the NIST team combined a fiber-coupled single photon source with a frequency up-conversion single photon detector. Both developed at NIST, the frequency up-conversion detector uses a strong pump laser and a special non-linear crystal to convert long wavelength (low frequency) photons into short wavelength (high frequency) photons with high efficiency and sensitivity (http://www.nist.gov/itl/antd/nir_082509.cfm).

According to Matthew Rakher and Kartik Srinivasan, two authors of the paper, previous up-conversion experiments looked at the color conversion of highly attenuated laser beams that contained less than one photon on average. However, these light sources still exhibited “classical” photon statistics exactly like that of an unattenuated laser, meaning that the photons are organized in such as way that at most times there are no photons while at other times there are more than one. Secure quantum communications relies upon the use of single photons.

“The quantum dot can act as a true single photon source,” says Srinivasan. “Each time we excite the dot, it subsequently releases that energy as a single photon. In the past, we had little control over the wavelength of that photon, but now we can generate a single photon of one color on demand, transmit it over long distances with fiber optics, and convert it to another color.”

Converting the photon's wavelength also makes it easier to detect, say co-authors Lijun Ma and Xiao Tang. While commercially available single photon detectors in the near-infrared suffer noise problems, detectors in the near-visible are a comparatively mature and high-performance technology. The paper describes how the wavelength conversion of the photons improved their detection sensitivity by a factor of 25 with respect to what was achieved prior to conversion.

*M. T. Rakher, L. Ma, O. Slattery, X. Tang, and K. Srinivasan. Quantum transduction of telecommunications band single photons from a quantum dot by frequency upconversion. Nature Photonics. Published online Oct. 3, 2010, doi:10.1038/nphoton.2010.221

Media Contact

Mark Esser EurekAlert!

More Information:

http://www.nist.gov

All latest news from the category: Physics and Astronomy

This area deals with the fundamental laws and building blocks of nature and how they interact, the properties and the behavior of matter, and research into space and time and their structures.

innovations-report provides in-depth reports and articles on subjects such as astrophysics, laser technologies, nuclear, quantum, particle and solid-state physics, nanotechnologies, planetary research and findings (Mars, Venus) and developments related to the Hubble Telescope.

Back to home

Comments (0)

Write a comment

Newest articles

Lighting up the future

New multidisciplinary research from the University of St Andrews could lead to more efficient televisions, computer screens and lighting. Researchers at the Organic Semiconductor Centre in the School of Physics and…

Researchers crack sugarcane’s complex genetic code

Sweet success: Scientists created a highly accurate reference genome for one of the most important modern crops and found a rare example of how genes confer disease resistance in plants….

Evolution of the most powerful ocean current on Earth

The Antarctic Circumpolar Current plays an important part in global overturning circulation, the exchange of heat and CO2 between the ocean and atmosphere, and the stability of Antarctica’s ice sheets….

Partners & Sponsors