麻豆淫院

(麻豆淫院Org.com) -- Scientists at the National Institute of Standards and Technology have developed the world's most efficient single photon detector, which is able to count individual particles of light traveling through fiber optic cables with roughly 99 percent efficiency. The team鈥檚 efforts could bring improvements to secure electronic communication, advanced quantum computation and the measurement of optical power.

Using essentially the same technology that permitted them to achieve 88 percent detection efficiency five years ago, the team has enhanced its ability to detect photons largely by improving the alignment of the detector and the optical fibers that guide photons into it. The basic principle of the detector is to use a superconductor as an ultra-sensitive thermometer. Each individual photon hitting the detector raises the temperature -- and increases electrical resistance -- by a minute amount, which the instrument registers as the presence of a photon.

According to team member Sae Woo Nam, the advantage of this type of single photon detector is that the new detector design not only measures lower levels of light than have ever been possible, but does so with great accuracy.

鈥淲hen these detectors indicate they鈥檝e spotted a photon, they鈥檙e trustworthy. They don鈥檛 give false positives,鈥� says Nam, a physicist with NIST鈥檚 Optoelectronics division. 鈥淥ther types of detectors have really high gain so they can measure a single photon, but their noise levels are such that occasionally a noise glitch is mistakenly identified as a photon. This causes an error in the measurement. Reducing these errors is really important for those who are doing calculations or communications.鈥�

The ability to count individual photons is valuable to designers of certain types of quantum computers as well as scientists engaged in quantum optical experiments, which concern exotic states of light that cannot be described by classical physics. But one of the most promising potential applications of a high-efficiency photon detector is a way to secure long-distance data transmission against unwanted interception. A detector that could recognize that a photon forming part of a transmission was missing would be a substantial defense against information theft.

The team has optimized the detection for 810 nanometers鈥攁n infrared wavelength鈥攁nd it still has high efficiency at other wavelengths that are interesting for fiber optic communications, as well as the quantum optics community. Ironically, the detector is so efficient that it outstrips current technology鈥檚 ability to determine its precise efficiency.

鈥淲e can鈥檛 be sure from direct measurement that we鈥檝e achieved 99 percent efficiency because the metrology is not in place to determine how close we are鈥攖here鈥檚 no well-established technique,鈥� Nam says. 鈥淲hat is great about our latest progress is that we measure nearly the same detection efficiency for every device we build, package and test. It鈥檚 the reproducibility that gives us confidence.鈥�

The team is currently working to develop evaluation techniques that can measure up to the detector鈥檚 abilities, and Nam says the team鈥檚 creation could also help evaluate other light-gathering devices.

鈥淣IST offers a standardized service for measuring the efficiency of photodetectors and optical power meters,鈥� he says. 鈥淲e鈥檙e trying to develop a calibration technique that extends to ultra-low levels of light. It should be valuable for anyone looking at single photons.鈥�