Device-independent conference key agreement from two-body correlators with balanced Dicke states
Abstract
Device-independent conference key agreement (DI-CKA) enables N > 2 distant parties to establish a common secret key without detailed characterization of the source or measurement devices. Many existing protocols rely on full-body Bell correlators, whose measurement can be demanding for a large number of parties. Here, we show that two-body correlators alone suffice for DI-CKA using balanced Dicke states for every even N ≥ 4. We construct two-body Bell inequalities and derive a tight analytical lower bound on the conditional von Neumann entropy by comparing their Bell operators with those of asymmetric Clauser-Horne-Shimony-Holt inequalities. In the ideal setting, certified key rates can approach $1-h[(N-2)/(4(N-1))]$, where h is the binary entropy function. This rate remains bounded away from zero as N → ∞, tending to 1−h(1/4) ≈ 0.189 bits per key-generation round. We show that the honest implementation of our protocol is invariant under collective phase noise. Moreover, a complementary full-body Bell construction certifies positive conference-key rates from correlations arbitrarily close to the local set.
Related
- Enhancing noise robustness in device-independent conference key agreement with asymmetric parity-CHSH inequalities
- Improving the Loss Tolerance of Heralded Photonic GHZ States for Long-Distance Device-Independent Conference Key Agreement
- Device-Independent Conference Keys from Parity-Extended Games
- From Claws to Conferences: Device-Independent Key Agreement Beyond Non-Signaling
- Pauli Error Composition Determines the Multipartite Advantage in Conference Key Agreement
BibTeX
@misc{ishihara2026deviceindependent,
title = {{Device-independent conference key agreement from two-body correlators with balanced Dicke states}},
author = {Makoto Ishihara and Masahiro Takeoka},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.41712},
eprint = {2610.41712},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.41712},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Device-independent conference key agreement from two-body correlators with balanced Dicke states
AU - Makoto Ishihara
AU - Masahiro Takeoka
PY - 2026
DA - 2026/10/30
PB - arXiv
DO - 10.48550/arxiv.2610.41712
UR - https://arxiv.org/abs/2610.41712
AB - Device-independent conference key agreement (DI-CKA) enables N > 2 distant parties to establish a common secret key without detailed characterization of the source or measurement devices. Many existing protocols rely on full-body Bell correlators, whose measurement can be demanding for a large number of parties. Here, we show that two-body correlators alone suffice for DI-CKA using balanced Dicke states for every even N ≥ 4. We construct two-body Bell inequalities and derive a tight analytical lower bound on the conditional von Neumann entropy by comparing their Bell operators with those of asymmetric Clauser-Horne-Shimony-Holt inequalities. In the ideal setting, certified key rates can approach $1-h[(N-2)/(4(N-1))]$, where h is the binary entropy function. This rate remains bounded away from zero as N → ∞, tending to 1−h(1/4) ≈ 0.189 bits per key-generation round. We show that the honest implementation of our protocol is invariant under collective phase noise. Moreover, a complementary full-body Bell construction certifies positive conference-key rates from correlations arbitrarily close to the local set.
ER -