Device-independent quantum key distribution (DI-QKD) enables two remote parties to share an information-theoretically secure key without any assumptions on the inner workings of the devices used. Device-independent conference key agreement (DI-CKA) is multipartite DI-QKD where more than two parties share a common secure key. The performance of DI-CKA, however, is strictly limited because of its susceptibility to losses due e.g. to imperfect detection efficiency and channel transmission. Here, we propose a DI-CKA protocol which reduces this limitation by using a heralding scheme to distribute multipartite entanglement. We analyze key rates of our protocol for two different measurement scenarios and we show that our protocol outperforms a previous DI-CKA protocol even with an experimentally feasible measurement.
@article{arxiv.2506.01296,
title = {Long-Distance Device-Independent Conference Key Agreement},
author = {Makoto Ishihara and Anders J. E. Bjerrum and Wojciech Roga and Jonatan B. Brask and Ulrik L. Andersen and Masahiro Takeoka},
journal= {arXiv preprint arXiv:2506.01296},
year = {2025}
}