We develop a silicon quantum processing unit utilizing a single electron spin as a qubit in lithographically defined quantum dot structures.
We aim to develop fundamental technologies for silicon-based fault tolerant quantum computing, including high-fidelity control of spin qubits and nano-fabrication of scaled-up qubit devices.

We develop a signal routing implementation technology applicable to the control of a large number of silicon qubits. Utilizing semiconductor circuit techniques and advanced chip packaging technology, we focus on developing a multi-channel, high-resolution signal generator and constructing signal paths to improve the integrity by using silicon interposers and through silicon vias. This approach is expected to address the complexities and increased wiring density associated with a growing number of qubits, thereby enhancing the scalability of silicon quantum processors.

　In our research, we are tackling the R & D of a middle-distance quantum information transfer. With this technology, it becomes possible to efficiently connect distant quantum bits.
　Our method uses voltage variations to transmit electron-spin quantum bits while maintaining the confinement of quantum dots. This allows for high-speed and reliable transmission of qubits. We plan to explore extending the transmission bus and adopting new methods to construct larger quantum systems and promote the integration of quantum bits.
　Our ultimate goal is to construct an on-chip quantum network, connecting high-performance, small-scale quantum processors, paving the way for advanced quantum computers.

　In order to achieve a scalable silicon quantum computer through the iterative implementation of elemental building blocks and mid-range quantum couplings, we develop an isotopically controlled Si/SiGe quantum platform to satisfy fault-tolerant requirements at the level of crystalline materials.
　In addition to implementation of ultra-high-quality Si isotope crystals with no scattering at the spatial scale of the qubit array units and quantum couplings, we promote development of atomic-scale interface control principles to mitigate the degradation of quantum controllability, and development of crystalline assessment schemes for isotopic substrates compatible with large-scale implementation.

We develop a quantum computer based on a new principle using electron wave packets propagating through quantum circuits.
A quantum bit is defined as a quantum state of an electron wave packet, and universal quantum operations are performed by repeatedly propagating the electron wave packet in a loop circuit where quantum operation circuits are embedded.This approach has the potential to construct a practical large-scale quantum computer with a small hardware realized using a single cryostat. The aim of this research item is to develop techniques for generating short electron wave packets of high quantum purity and high-fidelity quantum manipulation of qubits.

In this project, we will develop technologies to control the eigenstates of electron wave packets and to read out a single-electron wave packet as elemental technologies to realize a quantum computer based on a new principle using electron wave packets propagating in quantum circuits. The eigenstates of electron wave packets are usually controlled by controlling the width of the waveguide, but in this project, we will research and develop a new method using confinement of the electron wave packet in the direction of travel. In addition, we will develop a method to detect the presence or absence of electron wave packets by using electron spin qubits, which strongly interact with electron wave packets. We project the presence or absence of electron wave packets to the quantum state of electron spins. Then we detect electron wave packets by reading out the electro-spin state.