Optimality of universal conclusive entanglement concentration protocols

Abstract:Entanglement concentration is essential for quantum technologies, yet rigorous bounds on the success probability for universal protocols (those requiring no prior knowledge about the input state) have remained underexplored. We establish such fundamental limits for conclusive protocols distilling a perfect Bell state from pure two-qubit states by deriving the optimal success probability starting with two copies of a state with known Schmidt basis and four copies of a state with unknown Schmidt basis, using concatenated two-qubit operations. We prove that a known protocol achieves these bounds, confirming its optimality. Crucially, universality imposes an inherent efficiency trade-off, yielding an average success probability of just 2/105 over Haar measure.

arXiv:2509.09423 [quant-ph]

(or arXiv:2509.09423v2 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2509.09423 Focus to learn more arXiv-issued DOI via DataCite

https://doi.org/10.1103/bz3j-9njg Focus to learn more DOI(s) linking to related resources

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