To perform practical problem-size calculations with high precision, we will need large-scale quantum computers equipped with quantum error correction (QEC) mechanisms. A QEC mechanism continuously corrects errors that occur in the qubits responsible for data retention in a quantum computer, thereby preserving accurate information. When scaling up, key considerations include: what type of QEC mechanism can be built within the design constraints of the physical platform, and what level of precision is required for devices and control systems to ensure stable QEC functionality?

This research project aims to address these issues specifically in the context of implementing quantum computers based on nanofiber cavity QED technology, and to propose optimal design guidelines.

We have been working on two main areas: (1) improving the performance and proposing optimal designs for quantum computing devices based on cavity QED, and (2) elucidating the conditions necessary for building error correction mechanisms based on cavity QED.
In the first area, we have clarified the optimal cavity design for performing gates between atomic qubits trapped in cavities. We also proposed high-performance photon generators using cavity QED and evaluated the theoretical limits of gate performance. This research provides guidelines for device design policies and informs experimentalists about the beneficial extent to which experimental precision should be increased.

Our research in the second area provides guidelines on what conditions need to be achieved experimentally to build a stable error correction mechanism. For instance, we considered multiple cavity QED network structures (Fig. 2) and clarified the cavity performance required to achieve fault-tolerant quantum computing (FTQC) for each (Fig. 3). More recently, we have also proposed ways to relax FTQC conditions by devising error estimation algorythm specific to errors in cavity QED networks, and we have suggested measurement-based quantum computation with cavity QED network that makes FTQC conditions easier to achieve.