Professor Akira Furusawa of the University of Tokyo is indeed a renowned scientist in the field of quantum optics and quantum information. He has made significant contributions to the field, including the development of various quantum technologies.
However, it's important to note that quantum computing is an area of active research and development, and achieving large-scale quantum computers with a billion qubits is currently a significant technological challenge. While there have been advancements in optical quantum computing, it is still an emerging technology and has its own set of challenges to overcome.
It's difficult to definitively determine whether Professor Furusawa's claims are feasible or just hype without specific details about his research, the approach being used, and the progress made since I'm not interested in that topic as much as i used to and my answer might be a bit outdated. Quantum computing is a complex and rapidly evolving field, and achieving a billion qubits would require substantial breakthroughs in various aspects, including qubit stability, error correction, and scalability.
It's always important to approach such claims with a critical mindset and consider the progress and advancements in the broader quantum computing community as well. Ongoing research and collaborations in the field will ultimately determine the feasibility and potential of different quantum computing technologies.