  We investigate transient transport of electrons through a single-quantum-dot
controlled by a plunger gate. The dot is embedded in a finite wire that is
weakly coupled to leads and strongly coupled to a single cavity photon mode. A
non-Markovian density-matrix formalism is employed to take into account the
full electron-photon interaction in the transient regime. In the absence of a
photon cavity, a resonant current peak can be found by tuning the plunger gate
voltage to lift a many-body state of the system into the source-drain bias
window. In the presence of an $x$-polarized photon field, additional side peaks
can be found due to photon-assisted transport. By appropriately tuning the
plunger-gate voltage, the electrons in the left lead are allowed to make
coherent inelastic scattering to a two-photon state above the bias window if
initially one photon was present in the cavity. However, this photon-assisted
feature is suppressed in the case of a $y$-polarized photon field due to the
anisotropy of our system caused by its geometry.
