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New Wavelength Converter is the Future of Quantum Tech

05 October 2016

Yale University researchers in Professor of Electrical Engineering & Physics, Hong Tang's lab have just created a device that converts visible light to infrared light.

That may not seem like a big deal, but it is a crucial step in building practical quantum information technology.

Photo of chip from Hong Tang's lab, compared in size to a quarter (colors in chip are photographic artifacts). Picture courtesy of Xiang Guo.Photo of chip from Hong Tang's lab, compared in size to a quarter (colors in chip are photographic artifacts). Picture courtesy of Xiang Guo.

The wavelength converter, built on a chip, would allow quantum bits to be manipulated and then transmit that same information over long distances. The could potentially be built on a scale required for quantum computers as the technology advances.

“People want to use short wavelength photons – like 700 to 800 nanometers - to do quantum computation,” said Xiang Guo said, a graduate student in Tang’s lab and lead author of the article. However, in order to transmit that information over a long distance through optics fibers with low loss, they need to convert the photons to longer wavelengths of about 1,500 nanometers. Then, when it reaches its destination, the photon needs to be converted back to the shorter wavelength.

How it works

When lasers send two wavelengths of light into the device, the converter generates a third frequency that serves as the middle ground between the two. The device is made from aluminum nitride, which is key to the device’s success.

“We managed to make it very low loss, while retaining the nonlinearity,” said Guo.

The lab began using the material about five years ago, but found that it was very lossy, meaning information was lost in the transmission. To combat this, the team improved the material quality, making it more transparent to light and reducing the loss of photons scattering at the boundary of the device.

According to Guo, the device has achieved a 14% conversion rate. He said the research team’s next step is to work more on the device and improve its conversion rates.

“We want to increase it all the way to 70%, or even 90% or 100%,” he added.

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