Faithful Interconversions of Three‐Logic‐Qubit Entangled States Via Error‐Predicted Module in Decoherence‐Free Subspace
Ling‐Hui Li, Fang‐Fang Du · Advanced Quantum Technologies · 2025
Abstract The interconversion between different types of entangled states is an essential process. It is particularly important for tasks requiring specific forms of entanglement, as it greatly enhances the versatility, robustness, and efficiency of quantum systems. In the paper, deterministic schemes are proposed for interconversion between three‐logic‐qubit W state and three‐logic‐qubit Knill‐Laflamme‐Milburn state within a decoherence‐free subspace (DFS). The process of mutual transformation leverages the state‐selective nature of a quantum dot (QD) confined in a double‐sided microcavity, along with high‐fidelity, error‐predictable quantum control gates. Furthermore, the incorporation of single‐photon detectors helps to identify and mitigate potential failures arising from imperfect interactions between photons and the QD‐cavity system, thereby significantly enhancing experimental viability. In‐depth analyses of both protocols confirm that they can, in principle, achieve near‐unit fidelities and outstanding efficiencies. Additionally, the protocols offer advanced solutions to decoherence challenges through the use of DFS, paving the way for the development of practical quantum technologies.