  Quantum key distribution (QKD) can provide information theoretically secure
key exchange even in the era of quantum computer. However, QKD requires the
classical channel to be authenticated, and the current method is pre-sharing
symmetric keys. For a QKD network of $n$ users, this method requires $C_n^2 =
n(n-1)/2$ pairs of symmetric keys to realize pairwise interconnection. In
contrast, with the help of mature public key infrastructure (PKI) and
post-quantum cryptography (PQC) with quantum resistant security, each user only
needs to apply for a digital certificate from certificate authority (CA) to
achieve efficient and secure authentication for QKD. We only need to assume the
short-term security of the PQC algorithm to achieve the long-term security of
the distributed keys. Here, we experimentally verified the feasibility,
efficiency and stability of the PQC algorithm in QKD authentication, and
demonstrated the advantages when new users join the QKD network. Using PQC
authentication we only need to believe the CA is safe, rather than all trusted
relays. QKD combined with PQC authentication will greatly promote and extend
the application prospects of quantum safe communication.
