  The theoretically proven security of quantum key distribution (QKD) could
revolutionise how information exchange is protected in the future. Several
field tests of QKD have proven it to be a reliable technology for cryptographic
key exchange and have demonstrated nodal networks of point-to-point links.
However, so far no convincing answer has been given to the question of how to
extend the scope of QKD beyond niche applications in dedicated high security
networks. Here we show that adopting simple and cost-effective
telecommunication technologies to form a quantum access network can greatly
expand the number of users in quantum networks and therefore vastly broaden
their appeal. We are able to demonstrate that a high-speed single-photon
detector positioned at a network node can be shared between up to 64 users for
exchanging secret keys with the node, thereby significantly reducing the
hardware requirements for each user added to the network. This
point-to-multipoint architecture removes one of the main obstacles restricting
the widespread application of QKD. It presents a viable method for realising
multi-user QKD networks with resource efficiency and brings QKD closer to
becoming the first widespread technology based on quantum physics.
