  A fault-tolerant quantum processor may be configured using stationary qubits
interacting only with their nearest neighbours, but at the cost of significant
overheads in physical qubits per logical qubit. Such overheads could be reduced
by coherently transporting qubits across the chip, allowing connectivity beyond
immediate neighbours. Here we demonstrate high-fidelity coherent transport of
an electron spin qubit between quantum dots in isotopically-enriched silicon.
We observe qubit precession in the inter-site tunnelling regime and assess the
impact of qubit transport using Ramsey interferometry and quantum state
tomography techniques. We report a polarization transfer fidelity of 99.97% and
an average coherent transfer fidelity of 99.4%. Our results provide key
elements for high-fidelity, on-chip quantum information distribution, as long
envisaged, reinforcing the scaling prospects of silicon-based spin qubits.
