  We show that a quantum dot connected via tunnel barriers to superconducting
leads traps a continuously tunable and hence fractional charge. The fractional
charge on the island is due to particle-hole symmetry breaking and can be tuned
via a gate potential acting on the dot or via changes in the phase difference
across the island. We determine the groundstate, equilibrium, and excitation
charges and show how to identify these quantities in an experiment.
