Quantum conferencing enables multiple nodes within a quantum network to share a secure group key for private message broadcasting. The key rate, however, is limited by the repeaterless capacity to distribute multiparticle entangled states across the network. Currently, in the finite-size regime, no feasible schemes utilizing existing experimental techniques can overcome the fundamental rate-distance limit of quantum conferencing in quantum networks without repeaters. Here, we propose a practical, multi-field scheme that breaks this limit, involving virtually establishing Greenberger-Horne-Zeilinger states through post-measurement coincidence matching. This proposal features a measurement-device-independent characteristic and can directly scale to support any number of users. Simulations show that the fundamental limitation on the group key rate can be overcome in a reasonable running time of sending 1014 pulses. We predict that it offers an efficient design for long-distance broadcast communication in future quantum networks.
@article{arxiv.2407.00897,
title = {Multi-field quantum conferencing overcomes the network capacity limit},
author = {Yuan-Mei Xie and Yu-Shuo Lu and Yao Fu and Hua-Lei Yin and Zeng-Bing Chen},
journal= {arXiv preprint arXiv:2407.00897},
year = {2025}
}