Realization of a multi-node quantum network using diamond spin qubits: Part II – Experimental results

A future quantum internet can unlock fundamentally new technologies by sharing entangled states across the nodes of the network. In the past decade, many buildings blocks of such a network have been demonstrated. In particular, the heralded distribution of entanglement between two physically separated nodes has been achieved on various platforms. Here we report on the experimental realization of a multi-node quantum network. Our network consists of three quantum nodes with Nitrogen Vacancy (NV) electron spins as communication qubits. Additionally, the middle node makes use of a nuclear spin qubit that serves as a quantum memory.

In this presentation we discuss two demonstrations of the capabilities of the quantum network: the heralded generation of genuine multipartite entanglement – a Greenberger-Horne-Zeilinger (GHZ) state – across the three nodes; heralded entanglement swapping in the central node to obtain a Bell state between the outermost nodes. The latter demonstration is equivalent to the basic operation of a quantum repeater.

Our work serves as a proof of principle demonstration of a quantum network and enables the exploration of the first multi-node protocols.