  Coherent links between qubits separated by tens of micrometers are expected
to facilitate scalable quantum computing architectures for spin qubits in
electrically-defined quantum dots. These links create space for classical
on-chip control electronics between qubit arrays, which can help to alleviate
the so-called wiring bottleneck. A promising method of achieving coherent links
between distant spin qubits consists of shuttling the spin through an array of
quantum dots. Here, we use a linear array of four tunnel-coupled quantum dots
in a 28Si/SiGe heterostructure to create a short quantum link. We move an
electron spin through the quantum dot array by adjusting the electrochemical
potential for each quantum dot sequentially. By pulsing the gates repeatedly,
we shuttle an electron forward and backward through the array up to 250 times,
which corresponds to a total distance of approximately 80 {\mu}m. We make an
estimate of the spin-flip probability per hop in these experiments and conclude
that this is well below 0.01% per hop.
