  A periodically driven quantum capacitor may function as an on-demand single
electron source as it has recently been demonstrated experimentally. However,
the accuracy at which single electrons are emitted is not yet understood. Here
we consider a conceptually simple model of a quantum capacitor and find
analytically the noise spectrum as well as the counting statistics of emitted
electrons. We find that the failure rate of the capacitor can be arbitrarily
small when operated under favorable conditions. Our theoretical predictions may
be tested in future experiments.
