Nanoantenna Enables Advanced Quantum Communication and Data Storage

Researchers at Osaka University, along with collaborating partners, have fabricated a nanoantenna that can have big implications for ultra-secure, long-distance communication.

The recent study was published in Applied Physics Express.

The team substantially enhanced photon-to-electron conversion through a metal nanostructure, which will advance the development of technologies for sharing and processing data.

Transmitting Quantum Information Long Distance

Since classical computer information is based on simple on/off readouts, it’s fairly easy to use a technology called a repeater to amplify and transmit information over long distances. However, quantum information is more complex and based on secure readouts, such as electron spin. 

Semiconductor nanoboxes, or quantum dots, are materials that researchers have been looking at in order to store and transfer quantum information. With that said, quantum repeater technologies are limited in various ways, including the current approach to converting photon-based information to electron-based information. This process is highly inefficient, which is why the team of researchers set out to look for new ways to overcome this conversion and transfer problem.

The Nanoantenna

Rio Fukai is lead author of the study.

“The efficiency of converting single photons into single electrons in gallium arsenide quantum dots — common materials in quantum communication research — is currently too low,” Fukai says. “Accordingly, we designed a nanoantenna — consisting of ultra-small concentric rings of gold — to focus light onto a single quantum dot, resulting in a voltage readout from our device.”

One of the impressive results of this study is that the team was able to enhance photon absorption by a factor of up to 9 when compared to not using the nanoantenna. Most of the photogenerated electrons were not trapped when a single quantum dot was illuminated. Instead, they accumulated in impurities or other locations in the device. 

The excess electrons gave a minimal voltage readout that could be distinguished from the one generated by the quantum dot electrons. All of this means the device’s intended readout wasn’t disrupted.

Akira Oiwa is senior author of the research.

“Theoretical simulations indicate that we can improve the photon absorption by up to a factor of 25,” Oiwa says.” Improving the alignment of the light source and more precisely fabricating the nanoantenna are ongoing research directions in our group.”

This new research provides well-established nanophotonics to advance quantum communication and information networks. It could lead to new types of quantum technologies with potential applications in information security and data processing.