A nanoantenna for long-distance, ultra-secure communication
Researchers have improved the transfer efficiency between quantum
information carriers, in a manner that's based on well-established nanoscience and is compatible with upcoming advanced communication technologies

Date:
November 16, 2021
Source:
Osaka University
Summary:
Researchers have used a nanoantenna to focus light onto a single
semiconductor nanobox. This approach will enhance the utility of
quantum repeater technology currently under development for advanced
communication and data storage. Such technology is essential to
overcoming the limitations of classical computer information for
securely sharing information over long distances.



FULL STORY ========================================================================== Information storage and transfer in the manner of simple ones and zeros
-- as in today's classical computer technologies -- is insufficient
for quantum technologies under development. Now, researchers from Japan
have fabricated a nanoantenna that will help bring quantum information
networks closer to practical use.


==========================================================================
In a study recently published in Applied Physics Express, researchers from Osaka University and collaborating partners have substantially enhanced
photon- to-electron conversion through a metal nanostructure, which is
an important step forward in the development of advanced technologies
for sharing and processing data.

Classical computer information is based on simple on/off readouts. It's straightforward to use a technology known as a repeater to amplify and retransmit this information over long distances. Quantum information
is based on comparatively more complex and secure readouts, such
as photon polarization and electron spin. Semiconductor nanoboxes
known as quantum dots are materials that researchers have proposed for
storing and transferring quantum information. However, quantum repeater technologies have some limitations - - for example, current ways to
convert photon-based information to electron- based information are
highly inefficient. Overcoming this information conversion and transfer challenge is what the researchers at Osaka University aimed to address.

"The efficiency of converting single photons into single electrons
in gallium arsenide quantum dots -- common materials in quantum
communication research - - is currently too low," explains lead author
Rio Fukai. "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." The
researchers enhanced photon absorption by a factor of up to 9, compared
with not using the nanoantenna. After illuminating a single quantum dot,
most of the photogenerated electrons weren't trapped there, and instead accumulated in impurities or other locations in the device. Nevertheless,
these excess electrons gave a minimal voltage readout that was readily distinguished from that generated by the quantum dot electrons, and thus
didn't disrupt the device's intended readout.

"Theoretical simulations indicate that we can improve the photon
absorption by up to a factor of 25," says senior author Akira
Oiwa. "Improving the alignment of the light source and more precisely fabricating the nanoantenna are ongoing research directions in our group." These results have important applications. Researchers now have a means of using well-established nano-photonics to advance the prospects of upcoming quantum communication and information networks. By using abstract physics properties such as entanglement and superposition, quantum technology
could provide unprecedented information security and data processing in
the coming decades.

========================================================================== Story Source: Materials provided by Osaka_University. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Rio Fukai, Yuji Sakai, Takafumi Fujita, Haruki Kiyama, Arne Ludwig,
Andreas D. Wieck, Akira Oiwa. Detection of photogenerated single
electrons in a lateral quantum dot with a surface plasmon antenna.

Applied Physics Express, 2021; 14 (12): 125001 DOI:
10.35848/1882-0786/ ac336d ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211116103147.htm

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