  Quantum key distribution can provide information-theoretical secure
communication, which is now heading towards building the quantum secure network
for real-world applications. In most built quantum secure networks,
point-to-multipoint (PTMP) topology is one of the most popular schemes,
especially for quantum access networks. However, due to the lack of custom
protocols with high secret key rate and compatible with classical optical
networks for PTMP scheme, there is still no efficient way for a
high-performance quantum access network with a multitude of users. Here, we
report an experimental demonstration of a high-rate 16-nodes quantum access
network based on passive optical network, where a high-efficient coherent-state
PTMP protocol is novelly designed to allow independent secret key generation
between one transmitter and multiple receivers concurrently. Such
accomplishment is attributed to a well-designed real-time shot-noise
calibration method, a series of advanced digital signal processing algorithms
and a flexible post-processing strategy with high success probability. Finally,
the experimental results show that the average secret key rate is around 2.086
Mbps between the transmitter and each user, which is two orders of magnitude
higher than previous demonstrations. With the advantages of low cost, excellent
compatibility, and wide bandwidth, our work paves the way for building
practical PTMP quantum access networks, thus constituting an important step
towards scalable quantum secure networks.
