Genetic Algorithm for Phononic Crystals

Tokyo, Japan – The advent of quantum computers promises to revolutionize computing, solving complex problems exponentially faster than classical computers. However, today’s quantum computers face challenges such as maintaining stability and transporting quantum information. Phonons, which are quantized vibrations in periodic lattices, offer new ways to improve these systems by strengthening qubit interactions and enabling more reliable information conversion. Phonons also facilitate better Communication in quantum computers, enabling their interconnection in a network. Nanophononic materials, which are artificial nanostructures with specific phononic properties, will be essential for next-generation quantum networks and communication devices. However, designing phononic crystals with the desired vibrational characteristics at the nano- and micro-scale remains a challenge.

In a study recently published in the journal ACS NanoResearchers from the Institute of Industrial Science, The University of Tokyo have experimentally proven a new genetic algorithm for automatic inverse design — which generates a structure based on the desired properties — of phonon crystal nanostructures, which allows for the control of acoustic waves in the material. “Recent advances in artificial intelligence and inverse design offer the possibility of finding irregular structures that exhibit unique properties,” explains the study’s lead author, Michele Diego. Genetic algorithms use simulations to iteratively evaluate proposed solutions, with the best ones passing on their characteristics, or “genes,” to the next generation. Example devices designed and manufactured using this new method were tested using light scattering experiments to determine the effectiveness of the approach.

The team was able to measure vibrations on a two-dimensional phonic “metacrystal” that had a periodic arrangement of smaller designed units. They showed that the device allowed vibrations along one axis but not along the perpendicular direction, and could therefore be used for acoustic focusing or waveguides. “By extending the search for optimized structures with complex shapes beyond normal human intuition, it becomes possible to design devices with precise control over the propagation properties of acoustic waves, quickly and automatically,” says senior author Masahiro Nomura. This approach is expected to be applied to surface acoustic wave devices used in quantum computers, smartphones and other devices.

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The article “Tuning the phonon dispersion of a genetically designed nanophonon metasurface” was published in ACS Nano in DOI:10.1021/acsnano.4c01954.

About the Institute of Industrial Science, University of Tokyo

Institute of Industrial Science, The University of Tokyo (UTokyo-IIS) is one of the largest university research institutes in Japan. UTokyo-IIS consists of over 120 research laboratories, each headed by a faculty member, and has over 1,200 members (approximately 400 staff and 800 students) actively engaged in education and research. Its activities cover almost all areas of engineering. Since its establishment in 1949, UTokyo-IIS has been working to bridge the huge gaps that exist between academic disciplines and real-world applications.