  Massless Dirac particles cannot be confined by an electrostatic potential.
This is a problem for making graphene quantum dots but confinement can be
achieved with a magnetic field and here, general conditions for confined and
deconfined states are derived. There is a class of potentials for which the
character of the state can be controlled at will. Then a
confinement-deconfinement transition occurs which allows the Klein paradox to
be probed experimentally in graphene dots.
