The realization of a highly connected network of qubit registers is a central challenge for quantum information processing and long-distance quantum communication. Diamond spins associated with NV centers are promising building blocks for such a network as they combine a coherent optical interface (similar to that of trapped atomic qubits) with a local register of robust nuclear spin qubits . At the same time, the excellent control of NV centers allows for testing and demonstrating fundamental concepts in physics such as qubit steering by adaptive partial measurements .
Here we present our latest progress towards scalable quantum networks. We have recently realized unconditional teleportation between long-lived qubits residing in independent setups separated by 3 meter . The key innovation of our work is the complete separation of teleporter preparation and teleporter execution, as envisioned in the original proposal. This separation enables the use of lossy long-distance channels based on photons while maintaining a deterministic teleportation for each state inserted. In particular, a photonic channel is used to generate heralded remote entanglement between two nitrogen-vacancy (NV) center electronic spins , while the teleportation protocol solely exploits matter qubits that allow for a deterministic Bell state measurement. Using our latest figures of merit, prospects for realizing quantum repeaters, multi-node quantum networks and a loophole-free Bell test will be discussed.
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