Deterministic multi-qubit entanglement in a quantum network

The deterministic entanglement of two remote qubits has recently been demonstrated with microwave photons, optical photons and surface acoustic wave phonons. However, the deterministic generation and transmission of multi-qubit entanglement has not been demonstrated, primarily due to limited state transfer fidelities. Here, we report a quantum network comprising two separate superconducting quantum nodes connected by a 1 meter-long coaxial cable, where each node includes three qubits. By directly connecting the coaxial cable to one qubit in each node, we can transfer quantum states between the nodes with a process fidelity of 0.911. Using the high-fidelity communication link, we can prepare a three-qubit Greenberger-Horne-Zeilinger (GHZ) state in one node and deterministically transfer this state to the other node, with a transferred state fidelity of 0.656. We further deterministically generate a six-qubit GHZ state, globally distributed within the network, with a state fidelity of 0.722. The GHZ state fidelities are clearly above the threshold of 1/2 for genuine multipartite entanglement, and show that this architecture can be used to coherently link together multiple superconducting quantum processors, providing a modular approach for building large-scale quantum computers.