  We show how a quantum dot with a ballistic single-channel point contact to a
superconductor can be created by means of a gate electrode at the edge of a
quantum spin Hall insulator (such as an InAs/GaSb quantum well). A weak
perpendicular magnetic field traps a Majorana zero-mode, so that it can be
observed in the gate-voltage-averaged differential conductance <dI/dV> as a
4e^2/h zero-bias peak above a (2/3{\pi}^2 - 4)e^2/h background. The
one-dimensional edge does not permit the braiding of pairs of Majorana
fermions, but this obstacle can be overcome by coupling opposite edges at a
constriction, allowing for a demonstration of non-Abelian statistics.
