  We consider tunneling of spinless electrons from a single channel emitter
into an empty collector through an interacting resonant level of the quantum
dot. When all Coulomb screening of sudden charge variations of the dot during
the tunneling is realized by the emitter channel, the system is described with
an exactly solvable model of a dissipative qubit. We derive the correspondent
Bloch equation for its quantum evolution. We further use it to specify the
qubit transient dynamics towards its stationary quantum state after sudden
change of the level position. We demonstrate that the time-dependent tunneling
current characterizing this dynamics exhibits an oscillating behavior for a
wide range of the model parameters.
