  We perform a detailed study of the effect of finite bias and magnetic field
on the tunneling-induced decay of the state of a quantum dot by applying a
recently discovered general duality [PRB 93, 81411 (2016)]. This duality
provides deep physical insight into the decay dynamics of electronic open
quantum systems with strong Coulomb interaction. It associates the amplitudes
of decay eigenmodes of the actual system to the eigenmodes of a so-called dual
system with attractive interaction. Thereby, it predicts many surprising
features in the transient transport and its dependence on experimental control
parameters: the attractive interaction of the dual model shows up as sharp
features in the amplitudes of measurable time-dependent currents through the
actual repulsive system. In particular, for interacting quantum dots, the
time-dependent heat current exhibits a decay mode that dissipates the
interaction energy and that is tied to the fermion parity of the system. We
show that its decay amplitude has an unexpected gate-voltage dependence that is
robust up to sizable bias voltages and then bifurcates, reflecting that the
Coulomb blockade is lifted in the dual system. Furthermore, combining our
duality relation with the known Iche-duality, we derive new symmetry properties
of the decay rates as a function of magnetic field and gate voltage. Finally,
we quantify charge- and spin-mode mixing due to the magnetic field using a
single mixing parameter.
