Experimental Asynchronous Measurement-Device-Independent Quantum Cryptographic Conferencing.

The quantum cryptographic conferencing (QCC) protocol, which distributes identical secure keys to user groups, is a crucial component of the quantum network. Previous experimental works have implemented the measurement-device-independent (MDI) QCC, of which the key rate in an N-user network scales as R∼O(η^{N}). Building on the MDI QCC protocol, the asynchronous MDI QCC protocol theoretically integrates the mode-pairing scheme into QCC, significantly boosting the key rate to R∼O(η) in the ideal case, which is independent of the number of users, thus demonstrating greater application potential. Experimentally, in this Letter, we implement the three-user asynchronous MDI QCC network without phase locking by adopting the fast Fourier transform-based frequency difference estimation and the phase drift compensation technique. Finally, we achieve a key rate of about 4.470×10^{-9}  bits per pulse under a maximum overall loss of about 59.6 dB. This Letter provides a scalable solution for the development of large-scale quantum communication networks in the future.