Counting statistics of coherent population trapping in quantum dots

Destructive interference of single-electron tunneling between three quantum dots can trap an electron in a coherent superposition of charge on two of the dots. Coupling to external charges causes decoherence of this superposition, and in the presence of a large bias voltage each decoherence event transfers a certain number of electrons through the device. We calculate the counting statistics of the transferred charges, finding a crossover from sub-Poissonian to super-Poissonian statistics with increasing ratio of tunnel and decoherence rates.

Figure 1

Three quantum dots connected to a source and a drain reservoir. Reversible transitions (rate $T$) and irreversible transitions (rate $\Gamma$) are indicated by arrows.

Figure 2

Dependence of the Fano factor $\alpha$ on the normalized decoherence rate ${\Gamma }_{\varphi }∕T$ for three values of $\Gamma ∕T$.