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NIST demonstrates single photon source.


A NIST scientist has demonstrated the emission of individual photons photon /pho·ton/ (fo´ton) a particle (quantum) of radiant energy.

pho·ton (ft
 on demand, a major accomplishment in the development of "single photonics," which utilizes the photon as the fundamental particle fun·da·men·tal particle (fnd-mn of optical metrology. A low density of InGaAs quantum dots (QDs), semiconductor nanostructures with 10 nm to 20 nm dimensions, is grown on GaAs by molecular beam epitaxy A technique that "grows" atomic-sized layers on a chip rather than creating layers by diffusion.. Individual quantum dots are isolated by a mesa etch. A pulsed laser illuminates the QD sample, exciting electron-hole pairs that are captured by the QD. The electron and hole recombine re·com·bine (rkm-bn in the QD, emitting exactly one photon that is incident on an intensity interferometer An instrument that measures the wavelengths of light and distances. It transmits two radio signals or beams of light and uses the interference principle (how they reinforce or neutralize each other) to determine the measurement. with a 50/50 percent beamsplitter and photon counting detectors. A histogram histogram /his·to·gram/ (his´to-gram) a graph in which values found in a statistical study are represented by vertical bars or rectangles. of start-stop time intervals is recorded. At time interval zero, there is a very small peak compared to the peaks that are observed at multiples of the excitation laser repetition rate. This is the signature that the photons PHOTONS - PHysics, Optoelectronics, and Technology Of Novel Microresonator Structures are emitted one at a time (photon on demand). In contrast, when multiple QDs are excited simultaneously, the peak height at a time interval of zero is equal to that at other time intervals corresponding to the laser repetition rate.

Applications of the single photon turnstile are envisioned for the development of high-accuracy, quantum-based radiometry, in which laser power and energy measurements are calibrated by counting photons. Single photon sources are also critical components of quantum cryptography A future technology for encrypting data that draws on inherent properties of photons. It enables a secret key to be transmitted over a fiber-optic channel without detection., or quantum key distribution Delivering cryptographic keys to the required parties. See key management and QKD., an ultra-secure form of communication.

CONTACT: Rich Mirin, (303) 497-3455; mirin@boulder.nist.gov.
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Title Annotation:General Developments
Publication:Journal of Research of the National Institute of Standards and Technology
Article Type:Brief Article
Date:May 1, 2003
Words:246
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