  Solid-state approaches to quantum information technology are attractive
because they are scalable. The coherent transport of quantum information over
large distances, as required for a practical quantum computer, has been
demonstrated by coupling solid-state qubits to photons1. As an alternative
approach for a spin-based quantum computer, single electrons have also been
transferred between distant quantum dots in times faster than their coherence
time2, 3. However, there have been no demonstrations to date of techniques that
can coherently transfer scalable qubits and perform quantum operations on them
at the same time. The resulting so-called flying qubits are attractive because
they allow for control over qubit separation and non-local entanglement with
static gate voltages, which is a significant advantage over other solid-state
qubits in confined systems for integration of quantum circuits. Here we report
the transport and manipulation of qubits over distances of 6 microns within 40
ps, in an Aharonov-Bohm ring connected to two-channel wires that have a tunable
tunnel coupling between channels. The flying qubit state is defined by the
presence of a travelling electron in either channel of the wire, and can be
controlled without a magnetic field. Our device has shorter quantum gates,
longer coherence lengths (~86 {\mu}m at 70 mK), and shorter operation times
(~10 ps or 100 GHz) than other solid-state flying qubit implementations4, 5,
which makes our solid-state flying qubit potentially scalable.
