Superconductor Ups Single-Photon Detection Accuracy
BOULDER, Colo., Jan. 6, 2016 — Improving on earlier technology, a single-photon detector made of superconducting nanowires offers reduced temporal jitter with less demanding cooling requirements.
This greater precision at a higher temperature makes the new detector useful for communications research and experiments involving quantum entanglement and teleportation.
A colorized micrograph of a single-photon detector made of superconducting nanowires patterned on molybdenum silicide. The image is about 35 μm across. Courtesy of Verma/NIST.
Researchers at the National Institute of Standards and Technology (NIST) used an electron beam to pattern nanowires into a thin film made of the heat-tolerant ceramic superconductor molybdenum silicide (MoSi). Researchers from the University of Geneva in Switzerland and the Jet Propulsion Laboratory also contributed to the work.
The tiny boost in energy that occurs when a single photon hits is enough to make the nanowires briefly lose their superconducting capability and become normal conductors, signaling the event. Nanowire detectors are superfast, counting tens of millions of photons per second, and generating few false counts.
Jitter is defined as uncertainty in the arrival time of a photon. Creating a system with less jitter means that photons can be spaced more closely together but still be correctly detected. This could enable communications at higher bit rates, with more information transmitted in the same period.
Using more electrical current than a 2011 NIST design based on tungsten-silicon alloy, the new detector cuts jitter in half, from about 150 ps to 76 ps.
Light absorption and efficiency were enhanced by embedding the detector in a cavity made of gold mirrors and layers of other unreactive materials. Efficiency of 87 percent was demonstrated at 1542 nm, a wavelength used in telecommunications. The tungsten-silicon devices had 93 percent efficiency.
Additionally, the new detector can operate at 2.3 K, whereas the tungsten-silicon detector required cooling to <1 K.
"The higher operating temperature of MoSi [superconducting nanotube single-photon detectors] makes these devices promising for widespread use due to the simpler and less expensive cryogenics required for their operation," the researcher wrote in Optics Express (doi: 10.1364/OE.23.033792).
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