Quantum networks are physical devices that store, process, and transmit quantum information based on the laws of quantum mechanics. They are the foundation for achieving quantum communication and large-scale quantum computing. The research team at Tsinghua University has utilized dual type quantum bit encoding of the same ion to achieve a quantum network node without crosstalk for the first time internationally, which is of great significance for future quantum communication and large-scale quantum computing. The research findings were recently published in the international academic journal Nature Communications. Quantum networks can be implemented by different physical carriers, and ion traps are one of the most promising physical systems among them. Ion photon entanglement is a crucial step in implementing ion trap quantum networks, but this operation can affect ion storage bits and lead to information loss. To avoid this crosstalk phenomenon, researchers typically use different types of ions to generate ion photon entanglement and store quantum information separately, suppressing crosstalk errors. However, this method often requires high device costs, precise control of the proportion and position of different types of ions during operation, and low synergistic cooling efficiency between different ions, making operation difficult. The figure is a demonstration of a quantum network node without crosstalk (provided by the interviewee). Therefore, Professor Duan Luming's research group at the Cross Information Research Institute of Tsinghua University has creatively proposed a solution to use dual type quantum bits of the same ion to implement quantum network nodes after long-term research. Huang Yuanyuan, an assistant researcher at the Cross Information Research Institute of Tsinghua University, introduced that they use two pairs of ultra fine energy level structures of the same ion to encode "communication bits" used for entanglement with photons and "storage bits" used for storing information in quantum networks. At the same time, laser was used to achieve microsecond level coherent conversion between two types of quantum bits. The experiment found that the communication bits prepared by this method can generate ion photon entanglement in hundreds of milliseconds; The spin echo method can extend the storage life of stored qubits and achieve storage quantum bits with coherence time of seconds. By comparing the fidelity changes of stored bits with and without ion photon entanglement generation operations, researchers have confirmed that the crosstalk error between the two quantum bits is lower than the experimental accuracy, thus achieving a quantum network node without crosstalk. The picture shows Feng Lu (left), a doctoral student of the Institute of Cross Information Research of Tsinghua University, and Huang Yuanyuan (right), an assistant researcher, are studying in the laboratory (the picture is provided by the interviewees). Duan Luming, an academician of the CAS Member and a professor of the Institute of Cross Information Research of Tsinghua University, said that this new scheme greatly simplifies the experimental system in hardware compared with the previous scheme of using different kinds of ions to generate ion photon entanglement and store quantum information, Ensuring the effectiveness of information dissemination and storage has taken an important step towards the modularity of future quantum computers and quantum networks. (Lai Xin She)
Edit：Hou Wenzhe Responsible editor：WeiZe
Source：XinhuaNet
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