Associate Professor Shuntaro Takeda and his colleagues at the Graduate School of Engineering have succeeded in developing a unique photonic quantum processor that serves as the heart of a large-scale photonic quantum computer system. This time, the team developed and demonstrated the core circuit that Associate Professor Takeda and his colleagues had proposed in 2017 as a universal circuit that combines versatility and expandability not found in conventional circuits. Now, the photonic quantum computer, which has been a bottleneck in the development of large-scale quantum computers, will be able to run on the smallest circuits, and is expected to be developed into the ultimate large-scale quantum computer.This paper was published in the online edition of Science Advances on Thursday, November 12.