  Realizing robust quantum information transfer between long-lived qubit
registers is a key challenge for quantum information science and technology.
Here we demonstrate unconditional teleportation of arbitrary quantum states
between diamond spin qubits separated by 3 meters. We prepare the teleporter
through photon-mediated heralded entanglement between two distant electron
spins and subsequently encode the source qubit in a single nuclear spin. By
realizing a fully deterministic Bell-state measurement combined with real-time
feed-forward we achieve teleportation in each attempt while obtaining an
average state fidelity exceeding the classical limit. These results establish
diamond spin qubits as a prime candidate for the realization of quantum
networks for quantum communication and network-based quantum computing.
