Researchers from The University of Osaka have identified a novel design method for photonic circuitry used in quantum computers, potentially promoting mass production and scaling up

Osaka, Japan – Quantum computing represents a potential breakthrough technology that could far surpass the technical limitations of modern-day computing systems for some tasks. However, putting together practical, large-scale quantum computers remains challenging, particularly because of the complex and delicate techniques involved.

In some quantum computing systems, single ions (charged atoms such as strontium) are trapped and exposed to electromagnetic fields including laser light to produce certain effects, used to perform calculations. Such circuits require many different wavelengths of light to be introduced into different positions of the device, meaning that numerous laser beams have to be properly arranged and delivered to the designated area. In these cases, the practical limitations of delivering many different beams of light around within a limited space become a difficulty.

To address this, researchers from The University of Osaka investigated unique ways to deliver light in a limited space. This work revealed power-efficient nanophotonic circuit with optical fibers attached to waveguides to deliver six different laser beams to their destinations. The findings have been published in APL Quantum.

“Scalable, practical methods of configuring photonic circuits associated with trapped-ion quantum computers to allow the delivery of laser light have not yet been developed,” says an author Alto Osada. “To overcome this challenge, we wanted to create an efficient method that accounts for all trapping zones in an ion trap.”

As part of the research, the waveguides had to be split and rearranged in creative ways inside the circuitry to transmit the different laser beams to the correct locations. The designs also had to take into consideration the ability to turn laser beams off and on independently, while providing the highest possible power efficiency.

The resulting waveguide patterns take the appearance of complex, eye-catching tapestries as the laser beams cross over one another and move through the circuits.

“Our work shows that this approach can allow several hundred qubits on a single chip,” points out Alto Osada. Qubits refers to the basic units of quantum computing, upon which quantum algorithms run to tackle the real-world problems.

The researchers utilized two approaches to forming patterns, referred to as bubble sort and blockwise duplication. Both patterns were found to have advantages, with the researchers suggesting that the choice between the two would depend on factors such as the number of laser beams required and losses of photonic elements. This study successfully highlighted the feasibility and potential of using complex patterns of waveguides in circuitry to bring beams of light to trapped ions.

This research provides exciting implications that the same concept could be applied not only to quantum computing but to the fabrication of advanced optical systems, representing an important technological breakthrough with a wide range of applications.
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The article, “Integrated multi-wavelength photonic routing architectures for scalable trapped ion quantum devices,” was published in APL Quantum at DOI: https://doi.org/10.1063/5.0300216

About The University of Osaka
The University of Osaka was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world. Now, The University of Osaka is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.
Website: https://resou.osaka-u.ac.jp/en