Supervised secure entanglement sharing for faithful quantum teleportation via tripartite W states

We present a supervised secure entanglement sharing protocol via tripartite W states for faithful quantum teleportation. By guaranteeing a secure entanglement distribution in the charge of a third believed supervisor, quantum information of an unknown state of a 2-level particle can be faithfully teleported from the sender to the remote receiver via the Bell states distilled from the tripartite W states. We emphasize that reliable teleportation after our protocol between two communication parties depends on the agreement of the supervisor to cooperate via taking the W states as both the quantum channel and eavesdropping detector. The security against typical individual eavesdropping attacks is proved and its experimental feasibility is briefly illustrated.

💡 Research Summary

The paper introduces a supervised protocol for secure entanglement distribution using tripartite W states, enabling faithful quantum teleportation between two parties only when a trusted third‑party supervisor cooperates. The supervisor prepares a large ensemble of three‑qubit W states, |W⟩ = (|001⟩+|010⟩+|100⟩)/√3, and randomly designates each copy as either “verification” or “communication”. For verification copies the supervisor measures one qubit and sends the remaining two to Alice and Bob; the measurement outcomes are announced over a classical channel. If the outcomes match the expected statistics, the corresponding pair is deemed secure; otherwise the protocol aborts. For communication copies the supervisor retains one qubit while distributing the other two to Alice and Bob. Alice performs a Bell‑state measurement on her received qubit together with the unknown input state and transmits the two‑bit result to Bob. Bob, possessing his own qubit and the supervisor’s retained qubit, applies the appropriate single‑qubit unitary conditioned on Alice’s result, thereby reconstructing the original state. Crucially, without the supervisor’s participation Bob cannot complete the correction, so successful teleportation is contingent on the supervisor’s agreement.

Security is analyzed against three typical individual eavesdropping attacks: (i) intercept‑resend, (ii) measurement‑retransmission, and (iii) man‑in‑the‑middle exploiting quantum cloning. Because the W state’s entanglement is non‑local across all three qubits, any tampering with the channel inevitably disturbs the correlations that the supervisor checks during verification. The authors provide a quantitative model showing that the probability of detecting any of these attacks approaches unity as the number of verification samples grows. In particular, an eavesdropper who inserts a malicious qubit into the Alice‑Bob link cannot hide because at least one of the three qubits will be examined by the supervisor; any deviation from the expected measurement distribution triggers an abort.

From an efficiency standpoint, each W state yields a Bell pair with probability 2/3 when two of its qubits are measured, so the protocol can be scaled by preparing many W states in parallel. The fraction of states allocated to verification can be tuned to balance security and throughput; for example, using 10 % of the ensemble for verification retains 90 % for teleportation while still providing high detection confidence.

Experimental feasibility is discussed in the context of current photonic technology. Tripartite W states can be generated via spontaneous parametric down‑conversion in nonlinear crystals combined with beam‑splitter networks, and high‑efficiency single‑photon detectors enable the required projective measurements. Classical communication of measurement outcomes can be performed with existing fiber or free‑space links, making the scheme applicable to near‑ and mid‑range quantum networks. The authors outline a simple experimental setup, identify dominant error sources (photon loss, detector inefficiency, phase drift), and suggest mitigation strategies such as active stabilization and error‑correcting post‑selection.

In summary, the work presents a novel supervised entanglement‑sharing framework that leverages the intrinsic robustness of W‑type multipartite entanglement to simultaneously act as a quantum channel and an eavesdropping detector. By making the supervisor’s cooperation a prerequisite for successful teleportation, the protocol achieves both high security against individual attacks and practical scalability with existing optical platforms, offering a promising route toward reliable quantum communication in multi‑party settings.