Nanomechanical Oscillator Detects/Amplifies Microwaves


Devices used to amplify weak microwave signals have improved dramatically during the last 30 years with the development of such low noise solid-state devices such as the HEMT (high electron mobility transistor). Researchers at Aalto University School of Science in Finland have now come up with an entirely new way of detecting and amplifying microwave signals that adds the minimum amount of noise required by quantum mechanics.

The amplification takes place in a "nanomechanical oscillator," a very small device the University said resembles a miniature guitar string. The oscillator, a thousand times thinner than a human hair, is cooled to near absolute zero—minus 273 centigrade. At this temperature, all of the atoms in the resonator oscillate are in pace in their shared quantum state.

Researchers at the Low Temperature Laboratory at Aalto University discovered the effect when probing the device with a microwave laser.

A news release from the University said, "The discovery was actually quite unexpected. We were aiming to cool the nanomechanical resonator down to its quantum ground state. The cooling should manifest as a weakening of a probing signal, which we observed. But when we slightly changed the frequency of the microwave laser, we saw the probing signal to strengthen enormously. We had created a nearly quantum limited microwave amplifier, according to Academy Research Fellow Mika Sillanpää, who planned the project and made the measurements."

Academy Research Fellow Tero Heikkila explained "the beauty of the amplifier is in its simplicity: it consists of two coupled oscillators. Therefore, the same method can be realized in basically any media. By using a different structure of the cavity, one could detect terahertz radiation which would also be a major application."

More research is needed to make the amplifier suitable for real-life applications. Initially it is likely to be used in basic research on the borderline region between the everyday world and the quantum realm.

The research is detailed in the Nature article Microwave amplification with nanomechanical resonators. Although access to the full article is limited to subscribers, the preview portion indicates the device provided 25 dB of amplification with the addition of only 20 quanta of noise.

Doug Lung

Doug Lung is one of America's foremost authorities on broadcast RF technology. As vice president of Broadcast Technology for NBCUniversal Local, H. Douglas Lung leads NBC and Telemundo-owned stations’ RF and transmission affairs, including microwave, radars, satellite uplinks, and FCC technical filings. Beginning his career in 1976 at KSCI in Los Angeles, Lung has nearly 50 years of experience in broadcast television engineering. Beginning in 1985, he led the engineering department for what was to become the Telemundo network and station group, assisting in the design, construction and installation of the company’s broadcast and cable facilities. Other projects include work on the launch of Hawaii’s first UHF TV station, the rollout and testing of the ATSC mobile-handheld standard, and software development related to the incentive auction TV spectrum repack.
A longtime columnist for TV Technology, Doug is also a regular contributor to IEEE Broadcast Technology. He is the recipient of the 2023 NAB Television Engineering Award. He also received a Tech Leadership Award from TV Tech publisher Future plc in 2021 and is a member of the IEEE Broadcast Technology Society and the Society of Broadcast Engineers.