Efficient Quantum Conference Key Agreement over Quantum Networks

Quantum conference key agreement (CKA) is useful for many applications that involve secure communication or collaboration among multiple parties. While CKA over quantum networks can be achieved using pairwise quantum key distribution, a more efficient approach is to establish keys among the parties directly through multipartite entanglement distribution. Existing studies on multipartite entanglement distribution, however, are not designed for CKA, and hence do not aim to optimize key rate. In this paper, we first develop an efficient 3-party CKA strategy based on a closed-form expression that we derive for estimating errors. We then develop a general strategy for N-party CKA that accounts for estimated key rates on individual network paths. For both cases, we use multipath routing to improve key rate. We evaluate our approach in a wide range of settings and demonstrate that it achieves high key rate and degrades gracefully when increasing the number of parties.