All-electronic coherent population trapping in quantum dots

TL;DR

This paper demonstrates an all-electronic analogue of coherent population trapping in quantum dots, where destructive interference controls electron tunneling, enabling measurement of charge qubit coherence times.

Contribution

It introduces a fully electronic method to achieve and analyze coherent population trapping in quantum dots, linking current measurements to decoherence rates.

Findings

Current depends on decoherence rate and tunneling rates

Current peaks at inverse trapping time with increasing decoherence

Method enables measurement of charge qubit coherence time

Abstract

We present a fully electronic analogue of coherent population trapping in quantum optics, based on destructive interference of single-electron tunneling between three quantum dots. A large bias voltage plays the role of the laser illumination. The trapped state is a coherent superposition of the electronic charge in two of these quantum dots, so it is destabilized as a result of decoherence by coupling to external charges. The resulting current I through the device depends on the ratio of the decoherence rate Gamma_phi and the tunneling rates. For Gamma_phi --> 0 one has simply I=e Gamma_phi. With increasing Gamma_phi the current peaks at the inverse trapping time. The direct relation between I and Gamma_phi can serve as a means of measuring the coherence time of a charge qubit in a transport experiment.