Abstract Quantum entanglement is a cornerstone in the development of quantum information technology. In this paper, we propose two deterministic approaches for interconversion between the Λ-type three-atom Knill–Laflamme–Milburn (KLM) entangled state and the three-atom W state. Interconversion requires error-manifested parity-check gates (EMPCGs), leveraging interactions between the Λ-type atom–cavity system and an auxiliary photon. Additionally, the quantum circuit of the EMPCG ensures predictable function by transforming practical imperfections from photon scattering into failure-heralded detection events. Our analysis demonstrates that two reversible conversions not only achieve robust fidelity but also maintain high efficiency, thereby providing deeper insights into the fundamental nature of entanglement.
Abstract Quantum entanglement is a cornerstone in the development of quantum information technology. In this paper, we propose two deterministic approaches for interconversion between the Λ-type three-atom Knill–Laflamme–Milburn (KLM) entangled state and the three-atom W state. Interconversion requires error-manifested parity-check gates (EMPCGs), leveraging interactions between the Λ-type atom–cavity system and an auxiliary photon. Additionally, the quantum circuit of the EMPCG ensures predictable function by transforming practical imperfections from photon scattering into failure-heralded detection events. Our analysis demonstrates that two reversible conversions not only achieve robust fidelity but also maintain high efficiency, thereby providing deeper insights into the fundamental nature of entanglement.
Abstract Quantum entanglement plays a crucial role in quantum information technologies. In the paper, we propose two schemes to convert from two-photon Knill–Laflamme–Milburn (KLM) entangled states to Bell states and three-photon KLM state to Greenberger–Horne–Zeilinger states based on error-detected quantum devices (EDQDs), which employ the interaction between a quantum-dot-cavity system and a photon. Moreover, the quantum circuits of EDQDs applied in the conversion processes make our schemes carry out faithfully, as the practical photon-scattering deviations are changed into heralded-failure detections. Analyses show that conversion cases have unity fidelities and high efficiencies, which encourage us to appreciate deeply fundamental properties of entanglement.
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.
As the hyperentanglement of photon systems holds lots of remarkable applications for enhancing channel capacity with less quantum resource, the interconversion of various hyperentangled states warrants in-depth investigation and becomes a vital work for quantum information technologies. Here we realize completely mutual conversions between spatial-polarization hyperentangled Knill-Laflamme-Milburn state and hyperentangled W state for three-photon systems, resorting to hyperparallel quantum control gates and the practical nonlinear interaction of nitrogen-vacancy centers coupled with whispering-gallery-mode microresonators. The hyperparallel quantum gates, i.e., hyperparallel controlled-not and controlled-swap gates, are fundamental prerequisites for realizing interconversions of two hyperentangled states in a deterministic way. The fidelities of these conversion processes are robust and their efficiencies are also high due to fewer nonlinear interactions and errors heralded by the response of detectors, which intensify comprehending the properties of hyperentanglement.
The decoherence-free subspace (DFS) serves as a protective shield against certain types of environmental noise, allowing the system to remain coherent for extended periods of time. In this paper, we propose two protocols, i.e., one converts two-logic-qubit Knill-Laflamme-Milburn (KLM) state to two-logic-qubit Bell states, and the other converts three-logic-qubit KLM state to three-logic-qubit Greenberger-Horne-Zeilinger states, through cavity-assisted interaction in DFS. Especially, our innovative protocols achieve their objectives in a heralded way, thus enhancing experimental accessibility. Moreover, single photon detectors are incorporated into the setup, which can predict potential failures and ensure seamless interaction between the nitrogen-vacancy center and photons. Rigorous analyses and evaluations of two schemes demonstrate their abilities to achieve near-unit fidelities in principle and exceptional efficiencies. Further, our protocols offer progressive solutions to the challenges posed by decoherence, providing a pathway towards practical quantum technologies.
Abstract The generation, fusion, and interconversion of quantum entangled states play equally important roles in quantum information processing. In this paper, we propose a deterministic protocol to realize the interconversion between the three-electron-spin W state and the Knill–Laflamme–Milburn state by exploiting controlled quantum gates and parity-measuring devices constructed via the interaction between a photon and electron spins in silicon-vacancy system. Our analysis reveals that, considering non-ideal factors, both conversions achieve high fidelities and efficiencies. The efficient interconversion of stationary entangled states contributes to a deeper understanding of quantum entanglement and significantly contributes to quantum information processing
Abstract The interconversion of different types of entangled states not only can realize the information transmission but also play a significant role in quantum information technologies, including increasing scalability and computational power, and reducing error rates. Here, two protocols for achieving a complete interconversion between W state and Knill–Laflamme–Milburn state assisted by the quantum dot (QD)‐cavity systems and common quantum control gates are proposed. In particular, the protocols employ a heralded approach strategically designed to predict potential failures and facilitate seamless interaction between the QD‐cavity system and photons with the help of a single photon detectors, enhancing experimental accessibility. Through extensive analyzes and evaluations of two protocols, the proposed two protocols achieve remarkable utilization rates of photons (i.e., unit in principle) and achieve near‐unit fidelities and high efficiencies in principle.