Quantum secret sharing (QSS) is a multi-party quantum communication protocol that can be realized with bipartite entanglement and relative phase encoding. Previous implementations typically encoded the phase in the pump, applying it across the entire source bandwidth, thereby limiting scalability via wavelength multiplexing. In contrast, we present a variant of the standard QSS protocol that leverages frequency correlations to connect multiple users with a single source. The secret owner, who has access to the source, encodes classical information by applying frequency-dependent phase modulation to a broadband polarization-entangled photon pair. Each frequency channel, therefore, provides an independent QSS session among the secret owner and a pair of users. We demonstrate state fidelities of at least 90% for a channel pair of the 200 GHz ITU grid, a configuration that can be extended to more than 40 frequency bins for the same grid spacing. Notably, despite the use of large grid spacing and the experimental limitations, the system achieves full connectivity of a network of 7 users while maintaining a key fraction of 0.4 bits/photon. These results provide a resource-efficient path toward multi-user secret sharing over wavelength-multiplexed networks, eliminating the need for multiple two-photon or multi-photon sources.
Quantum secret sharing (QSS) is a multi-party quantum communication protocol that can be realized with bipartite entanglement and relative phase encoding. Previous implementations typically encoded the phase in the pump, applying it across the entire source bandwidth, thereby limiting scalability via wavelength multiplexing. In contrast, we present a variant of the standard QSS protocol that leverages frequency correlations to connect multiple users with a single source. The secret owner, who has access to the source, encodes classical information by applying frequency-dependent phase modulation to a broadband polarization-entangled photon pair. Each frequency channel, therefore, provides an independent QSS session among the secret owner and a pair of users. We demonstrate state fidelities of at least 90% for a channel pair of the 200 GHz ITU grid, a configuration that can be extended to more than 40 frequency bins for the same grid spacing. Notably, despite the use of large grid spacing and the experimental limitations, the system achieves full connectivity of a network of 7 users while maintaining a key fraction of 0.4 bits/photon. These results provide a resource-efficient path toward multi-user secret sharing over wavelength-multiplexed networks, eliminating the need for multiple two-photon or multi-photon sources.
Source-independent quantum secret sharing (SI QSS), while essential for secure multiuser cryptographic operations in quantum networks, faces significant implementation challenges stemming from the inherent complexity of generating and distributing multipartite entangled states. Recently, a resource-efficient SI QSS protocol utilizing entangled photon pairs combined with a postmatching method has been proposed to address this limitation. In this Letter, we report an experimental demonstration of this protocol using high-fidelity polarization-entangled photon pairs in a star topology. For a three-user network, we obtain secure key rates of 21.18, 4.69, and 1.71 kbps under single-user channel losses of 7.6, 10.9, and 12.9 dB respectively. Furthermore, under conditions of equal channel loss per user, we achieve secure key rates of 6.97, 6.46, and 5.88 kbps for three-, four-, and five-user scenarios respectively. These results demonstrate the advantageous independence of the key rate from the number of users. Our work paves the way for large-scale deployment of SI QSS in multiuser quantum networks.
Abstract Quantum secret sharing (QSS), as a fundamental cryptographic protocol for future quantum networks, continues to face significant challenges, particularly in the generation of multipartite entanglement and the degradation of entanglement fidelity during distribution, both of which severely limit its scalability. These persistent constraints motivate an alternative approach based on continuous-variable (CV) systems. We propose a CVQSS scheme based on an electro-optically modulated optical frequency comb. The scheme employs a single laser to generate multi-wavelength coherent states, enabling the efficient and flexible construction of secret sharing subnetworks. By incorporating a broadcast-based distribution mechanism, the architecture is scalable to 128 players. Experimental verification with 24 players over a 10 km fiber link demonstrates a secret sharing rate of 6.24 per player under asymptotic conditions and 1.27 Mbps per player under finite-size effects, and a 1.05MB image is secretly shared to six players. This work achieves information-theoretically secure QSS both within and across subnetworks, providing a solid technical foundation for the development of scalable and multifunctional quantum networks.
Quantum secret sharing (QSS) has emerged as a promising avenue for storing secret with quantum-enhanced security. However, practical applications are hindered by the challenge for simultaneously implementing high-efficiency, high-security, and high-flexibility QSS with multiple users. Here we present an efficient, secure, and flexible QSS involving eight users with a continuous-variable eight-partite bound entanglement (BE) state, where only two nondegenerated optical parameter amplifiers are required. Such abilities are attributed to the generation of the eight-partite BE state with precise phase controlling systems and a large entanglement network, and fiber distribution with polarization-division multiplexing. In the QSS, a higher key rate can be demonstrated, when a secret is extracted through flexible combinations of more collaborative users. Our system may pave the way for the spatially separated multiuser quantum communications, while minimizing quantum hardware. Published by the American Physical Society 2024
Quantum secret sharing (QSS) is a cryptographic multiparty communication technique in which a secret is divided and shared among N parties and then securely reconstructed by (N-1) cooperating parties, making it perfect for storing and sharing highly sensitive data. Challenges in high dimensional state preparation, transformation and detection, the key steps of any QSS protocol, have so far hindered experimental realisation. Here, by taking advantage of the high-dimensional encoding space accessible by a photon's orbital angular momentum, we present a toolbox for realising practical high-dimensional single photon QSS schemes that are easily scalable in both dimension and number of participants. Our implementations realised a new record in both the number of participants (N=10) and the dimensionality (d=11), with the latter facilitating the transfer of 2.89 bits of information per photon. This work is an important step towards securely distributing information across a network of nodes.
Large-scale quantum networks require dynamic and resource-efficient solutions to reduce system complexity with maintained security and performance to support growing number of users over large distances. Current encoding schemes including time-bin, polarization, and orbital angular momentum, suffer from the lack of reconfigurability and thus scalability issues. Here, we demonstrate the first-time implementation of frequency-bin-encoded entanglement-based quantum key distribution and a reconfigurable distribution of entanglement using frequency-bin encoding. Specifically, we demonstrate a novel scalable frequency-bin basis analyzer module that allows for a passive random basis selection as a crucial step in quantum protocols, and importantly equips each user with a single detector rather than four detectors. This minimizes massively the resource overhead, reduces the dark count contribution, vulnerability to detector side-channel attacks, and the detector imbalance, hence providing an enhanced security. Our approach offers an adaptive frequency-multiplexing capability to increase the number of channels without hardware overhead, enabling increased secret key rate and reconfigurable multi-user operations. In perspective, our approach enables dynamic resource-minimized quantum key distribution among multiple users across diverse network topologies, and facilitates scalability to large-scale quantum networks.
Quantum secret sharing (QSS) is a typical multi-party quantum communication mode, in which the key sender splits a key into several parts and the participants can obtain the key by cooperation. Measurement-device-independent quantum secret sharing (MDI-QSS) is immune to all possible attacks from measurement devices and can greatly enhance QSS’s security in practical applications. However, previous MDI-QSS’s key generation rate is relatively low. Here, we adopt the polarization-spatial-mode hyper-encoding technology in the MDI-QSS, which can increase single photon’s channel capacity. Meanwhile, we use the cross-Kerr nonlinearity to realize the complete hyper-entangled Greenberger–Horne–Zeilinger state analysis. Both above factors can increase MDI-QSS’s key generation rate by about 103. The proposed hyper-encoded MDI-QSS protocol may be useful for future multiparity quantum communication applications.