  We study entanglement of charge qubits in a vertical tunnel-coupled double
quantum dot containing two interacting electrons. Exact diagonalization is used
to compute the negativity characterizing entanglement. We find that
entanglement can be efficiently generated and controlled by sidegate voltages,
and describe how it can be detected. For large enough tunnel coupling, the
negativity shows a pronounced maximum at an intermediate interaction strength
within the Wigner molecule regime.
