Experimental quantum conference key agreement

Abstract

Quantum networks will provide multinode entanglement enabling secure communication on a global scale. Traditional quantum communication protocols consume pair-wise entanglement, which is suboptimal for distributed tasks involving more than two users. Here, we demonstrate quantum conference key agreement, a cryptography protocol leveraging multipartite entanglement to efficiently create identical keys between N users with up to N-1 rate advantage in constrained networks. We distribute four-photon Greenberger-Horne-Zeilinger (GHZ) states, generated by high-brightness telecom photon-pair sources, over optical fiber with combined lengths of up to 50 km and then perform multiuser error correction and privacy amplification. Under finite-key analysis, we establish 1.5 × 106 bits of secure key, which are used to encrypt and securely share an image between four users in a conference transmission. Our work highlights a previously unexplored protocol tailored for multinode networks leveraging low-noise, long-distance transmission of GHZ states that will pave the way for future multiparty quantum information processing applications.

Quantum Conference Key Agreement: A Review

“…A thermalised interacting photon gas [123] may also prove to be a suitable source of genuine multipartite entanglement. Recently, the first quantum CKA protocol has been implemented [124] among four parties. The experiment is based on the multiparty BB84 protocol [65] discussed in Section III A.…”

Authentication of variable length messages in quantum key distribution

“… As universal hashing is used not only for authentication in QKD but also in other steps in QKD like error correction and privacy amplification [ 7 , 13 , 25 – 30 ], our constructions and results might lead to improvements in QKD protocols, among other areas. Universal hash functions have been recently used in studying quantum secure direct communication (QSDC) [ 75 ] (see also, [ 76 – 80 ]), quantum secret sharing (QSS) (either directly [ 81 , 82 ] or via a security proof based on QKD [ 83 ]), quantum conference key agreement (QCKA) [ 84 – 86 ], and quantum authentication [ 87 – 89 ]. Therefore, our efficient and secure constructions and results might lead to improvements in these directions as well.…”

“…Universal hash functions have been recently used in studying quantum secure direct communication (QSDC) [ 75 ] (see also, [ 76 – 80 ]), quantum secret sharing (QSS) (either directly [ 81 , 82 ] or via a security proof based on QKD [ 83 ]), quantum conference key agreement (QCKA) [ 84 – 86 ], and quantum authentication [ 87 – 89 ]. Therefore, our efficient and secure constructions and results might lead to improvements in these directions as well.…”

High-Dimensional Quantum Conference Key Agreement

“…Quantum conference key agreement (QCKA) protocols are designed to allow multiple parties to establish a common, shared, secret key secure against computationally unbounded adversaries. Starting from early work in this field [4,5], QCKA protocols have advanced substantially with new protocols and security proofs [6,7,8]; it is also experimentally feasible [9]. Interestingly, it has been shown that there are some scenarios where such multiparty protocols hold an advantage over the naive use of multiple two-party protocols run in parallel [5].…”