Chinese scientists have made an advance in quantum networking by achieving, for the first time, a crosstalk-avoided quantum network node using dual-type qubits of the same ion species.

Qubit, or quantum bit, is the basic unit of information in quantum computing. One of the current most promising physical systems for quantum networks is ion trap. In such a network, the ion-photon entanglement is the basic unit, but it would affect memory qubits carrying quantum information and cause an information loss, which is known as crosstalk.

To avoid the crosstalk, two ion species are commonly used to, respectively, entangle with photons and store quantum information. However, this dual-species scheme has limitations such as high device cost for different ions and high requirements for operations.

A research team from Tsinghua University proposed a quantum network node where only a single ion species was needed, but with two types of its qubits. They published the findings recently in the journal Nature Communications.

In the findings, the same kind of ions in the quantum network node were encoded in two different hyperfine structure levels, one for entanglement with photons and the other for information storage, said Huang Yuanyuan, a team member at Tsinghua University.

Huang noted the ion-photon entanglement was generated in a typical timescale of hundreds of milliseconds, and its crosstalk on the memory qubit was verified to be negligible at the experimental precision.

The new scheme, on the premise of ensuring the effect of ion-photon entanglement and information storage, has greatly simplified the hardware system of quantum networking and taken a significant step towards its future development, said Duan Luming, the team leader at Tsinghua University.

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