  Quantum communication is developed owing to the theoretically proven security
of quantum mechanics, which may become the main technique in future information
security. However, most studies and implementations are limited to two or
several parties. Herein, we propose a fully connected quantum communication
network without a trusted node for a large number of users. Using flexible
wavelength demultiplex/multiplex and space multiplex technologies, 40 users are
fully connected simultaneously without a trusted node by a broadband
energy-time entangled photon pair source. This network architecture may be
widely deployed in real scenarios such as companies, schools, and communities
owing to its simplicity, scalability, and high efficiency.
