Increasing entanglement concentration and the role of measurement imaginarity
Phys. Rev. A 113, 062439 – Published 15 June, 2026
DOI: https://doi.org/10.1103/jld4-y6q5
Abstract
The role of complex numbers in quantum theory extends beyond mathematical convenience, having recently been formalized as a resource under the framework of the resource theory of imaginarity. Operationally, imaginarity translates into using more resources in linear optical setups. In this work, we investigate the operational advantage offered by complex-valued measurements in the entanglement of assistance protocol for three-qubit systems. We demonstrate that employing such measurement bases leads to a significant improvement in the concentration of bipartite entanglement with the aid of the third party. We further analyze a modified entanglement swapping protocol and show that three-qubit complex measurement bases with certain symmetries outperform the standard Greenberger-Horne-Zeilinger basis. This is also one example where a three-qubit nonmaximally entangled basis surpasses a maximally entangled one in generating entanglement. Construction of the basis also addresses the open problems raised by Pimpel et al. [F. Pimpel et al., Phys. Rev. A 108, 022220 (2023)]. As an intriguing application, we show that using this approach in quantum network percolation on a honeycomb lattice reduces the required bond occupation probability by and the requirement of entanglement by in each bond.
