Progress Report
Fault-tolerant Quantum Computing with Photonically Interconnected Ion Traps[5] Research and development on integrated optical circuits for ion trapping
Progress until FY2024
1. Outline of the project
Many kinds of lasers are utilized in trapped-ion quantum technology. Conventional implementations of light sources are free-space optical circuits with many optical elements mounted on a rigid optical table. However, our R&D project aims at replacing previous system with a photonic circuit fabricated on a tiny chip, which leads to the realization of a “photonically integrated ion trap.” Such a technological development can drastically promote the compact and stable implementation of a trapped-ion quantum node, and facile reproduction of it is indeed necessary for a photonically interconnected ion-trap quantum computer.
2. Outcome so far
At Kyushu University, we are developing integrated photonic circuits to introduce multiple laser sources for ion excitation into ion traps. These lasers span a broad spectral range from the visible to the near-infrared, and up to six laser wavelengths need to be focused into the ion trap. To realize such optical components, we have employed high-precision optical waveguide fabrication technologies. Silicon nitride (SiN) offers excellent photonic integration properties, making it suitable for realizing monolithic ion trap devices with integrated optical circuits. We are now entering the final stage of modular integration with the ion trap device currently under development at Osaka University. Once completed, optical injection experiments—previously requiring large-scale experimental setups—will become feasible using a single compact photonic chip.
In parallel, the group at Osaka University has been working on the complementary development of integration techniques for ion traps with built-in optical circuits, as well as on the fabrication technologies for implementing these circuits on photonic chips. They have also designed, prototyped, and evaluated optical emission components for selectively irradiating a single trapped ion with laser light. Moving forward, final adjustments will be made to implement the optical components into the integrated ion trap platform, with the goal of achieving full system modularization.
3. Future plans
Moving forward, we will fabricate an integrated photonic ion trap by incorporating the previously designed and evaluated optical emission components directly into the ion trap device, advancing our research toward the completion of a fully modular ion trap system. We will continue to pursue the cutting edge of a new interdisciplinary field that merges ion-trap quantum technology with photonics, aiming to achieve a significant breakthrough in the miniaturization of quantum nodes.