  Quantum cryptography is a major ingredient of the future quantum internet
that promises various secure communication tasks. Quantum conference key
agreement (CKA) is an important cryptographic primitive of quantum
cryptography, which provides the conference key among multiple users
simultaneously. However, quantum CKA is currently far from practical
application due to the low conference key rate. Here, we propose a quantum CKA
protocol of three users with information-theoretic security. Our protocol only
requires phase-randomized weak coherent sources and threshold single-photon
detectors, and is anticipated to be experimentally demonstrated over 600 km
under current technology. Our scheme can be widely implemented in the
approaching large-scale quantum network.
