This project aims at developing technology bases for implementing scalable qubit devices toward realization of semiconductor quantum computers. To achieve this target, we employ sparse integration of multi-qubit devices and middle-distance quantum links to fabricate qubit unit structures and then assemble them on high-quality silicon/silicon-germanium (Si/SiGe) substrate. An important challenge here is to establish technology bases for implementing multi-qubit devices in collaboration with industry. The integration of multi-qubits mediated by middle-distance quantum links completely differs from conventional methods. In addition, we are developing quantum computing based on new principles for controlling electron wave-packets as propagating qubits.

Currently in the first year of the project we are installing various equipment of electronics, big dilution refrigerators and crystal growth. In parallel we are making a prototype of small-scale qubit unit structures as elements to construct scalable multi-qubit devices, designing quantum channels suitable for the quantum links, developing a method of controlling hetero-interfaces to realize high-quality silicon substrates, and performing basic experiments to generate electron wave-packets.

We fabricate and characterize qubit device prototypes to optimize the qubit unit structures. Based on this result we will challenge ourselves to build the technology bases for implementing scalable multi-qubit devices in collaboration with industry. In addition, we demonstrate robust quantum coherence of electron wave packets to indicate the usefulness of the wave-packet qubits. Achievement of these issues will lead to realization of fault-tolerant quantum computers.