  The computational power and fault-tolerance of future large-scale quantum
processors derive in large part from the connectivity between the qubits. One
approach to increase connectivity is to engineer qubit-qubit interactions at a
distance. Alternatively, the connectivity can be increased by physically
displacing the qubits. This has been explored in trapped-ion experiments and
using neutral atoms trapped with optical tweezers. For semiconductor spin
qubits, several studies have investigated spin coherent shuttling of individual
electrons, but high-fidelity transport over extended distances remains to be
demonstrated. Here we report shuttling of an electron inside an isotopically
purified Si/SiGe heterostructure using electric gate potentials. First, we form
static quantum dots, and study how spin coherence decays as we repeatedly move
a single electron between up to five dots. Next, we create a traveling wave
potential to transport an electron in a moving quantum dot. This second method
shows substantially better spin coherence than the first. It allows us to
displace an electron over an effective distance of 10 {\mu}m in under 200 ns
with an average fidelity of 99%. These results will guide future efforts to
realize large-scale semiconductor quantum processors, making use of electron
shuttling both within and between qubit arrays.
