A key step towards acoustic integrated circuits: Sound waves can be controlled and modulated on a chip for the first time

A chip that can control and modulate sound waves. Image credit: Shao Linbo/Harvard University

Scientists from Harvard University in the United States wrote in the latest issue of Nature Electronics magazine that they have demonstrated for the first time how to use electric fields to control and modulate sound waves on a chip, which is one step closer to the ultimate development of acoustic integrated circuits.

The researchers pointed out that although sound waves are slower than electromagnetic waves of the same frequency, they also have their own advantages: short sound waves are easily confined in nanoscale structures, do not easily "talk" to each other, and have strong interactions with the system that confines them, which makes them widely applicable to classical and quantum computing systems.

"Acoustic waves are promising information carriers for both quantum and classical information processing chips, but scientists have been unable to control them in a low-loss, scalable way, which has hampered the development of acoustic integrated circuits," said Marco Ronca, a professor of electrical engineering at the Harvard School of Engineering and Applied Sciences (SEAS) and senior author of the latest study. "In this latest study, we demonstrated that acoustic waves can be controlled on an integrated lithium niobate platform, bringing us one step closer to acoustic integrated circuits."

Lonca and his team used the unique properties of lithium niobate to build an on-chip electroacoustic modulator to control the propagation of sound waves in an on-chip waveguide. The study showed that by applying an electric field, the modulator can control the phase, amplitude and frequency of the sound waves on the chip.

“This work advances the use of sound waves for both quantum and classical computing,” said Linbo Shao, a former SEAS postdoctoral fellow and first author of the paper. “Previous acoustic devices were passive, but now we can actively tune acoustic devices using electric fields. This paves the way for high-performance acoustic-wave-based devices and circuits that can be used for next-generation microwave signal processing, as well as on-chip quantum networks and interfaces that connect different types of quantum systems, including solid-state atomic systems and superconducting qubits.”

The researchers said that while they have only demonstrated a device on a chip, they are working to build more complex, large-scale acoustic wave circuits and interconnect with other quantum systems such as diamond color centers. Diamond color centers refer to nitrogen-vacancy color centers in diamond, which are the most common point defects in the diamond crystal structure and the most representative quantum system at present.