A research group led by Professor Xifeng Ren at Hefei Laboratory/ University of Science and Technology of China (USTC) has successfully demonstrated the teleportation of a quantum controlled-NOT (CNOT) gate between two quantum photonic integrated chips for the first time. This work was published on July 8th in the journal Physical Review Letters.

Building large-scale quantum networks hinges on creating highly integrated, scalable quantum nodes and achieving high-fidelity quantum interconnections between them. Quantum photonic integrated chips are a highly promising platform for such networks. Within these networks, performing quantum gate operations between qubits at different nodes is crucial. Among these, teleporting a high-fidelity CNOT gate to entangle remote qubits is particularly challenging and represents a core step for distributed quantum computing. The implementation process is complex: it requires sharing entangled photon pairs between the two quantum nodes and executing high-precision, complex on-chip linear optical quantum operations within each node, placing extremely high demands on device performance.

To address these challenges, the research team prepared quantum entanglement sources based on silicon photonic chips and transmitted one photon from a pair to the other chip via a single-mode optical fiber. Critically, the team employed high-dimensional quantum information encoding techniques, which significantly simplified the linear optical quantum operations required within each individual node, thereby ensuring the successful realization of the chip-to-chip CNOT gate teleportation.

The team verified the performance of the teleported quantum logic gate using quantum state tomography and quantum process tomography techniques. With a 5-meter fiber interconnection, the teleported state fidelity reached 95.69%, and the gate process fidelity was 94.81%. Even when the fiber link was extended to 1 kilometer, the state fidelity remained high at 94.07%, with a gate process fidelity of 93.04%.

This achievement marks a significant breakthrough in realizing core quantum logic operations between quantum photonic integrated chips. The ability to maintain such high fidelity for CNOT gate teleportation over kilometer-scale distances lays a solid technical foundation for building large-scale quantum networks based on quantum photonic integrated chips and for implementing quantum information processing tasks such as distributed quantum computing.

This research was supported by the Ministry of Science and Technology of China, the National Natural Science Foundation of China, Anhui Province, and the University of Science and Technology of China.