Figure 3: The relative occupation τ$_{e}$/τ$_{c}$ versus the inverse of the nominal temperature 1 /T . We demonstrate that in our sample the detailed balance holds down to the nominal value of 600 mK. The sample was operated at V$_{G}$ =495.4 mV and V$_{d}$ =-9 mV and it carried a current of about 15 nA. Inlet: the current switching as function of time at the lowest temperature. The current shift Δ I is 0.9 nA. 8