ULTRAQUEST · Ultrafast quantum transport in nanosystems controlled via phase-locked single cycles of light

The aim of the project consists in starting new experiments in which the absolute optical phase of quasi single-cycle light pulses is harnessed to directly control charge transport in quantum nanosystems. The basic concept of this technique relies on the fact that, with ultrashort pulsed laser sources, it is possible to obtain extremely high peak intensities and thus high peak electric fields. Such pulses can be focused on a nano-scale junction of an electronic circuit. The strong field then allows symmetry breaking of the electronic band structure and triggers charge tunneling from one side of the junction to the other one through the potential barrier of the dielectric medium. Since this effect depends nonlinearly on the bias field, a net current results in the limit of phase-locked excitation pulses thus giving rise to temporal resolution and control on the sub-cycle timescale. In this project we want to exploit the described phenomenon in a regime in which it would be possible to study ultrafast electron transport in nanosystems with strong quantum confinement. To this end, we plan to fabricate nanostructured plasmonic junctions in patterned circuits loaded with single quantum systems such as semiconductor quantum dots. To study the quantum charge transport on such systems we need extremely high sensitivities and a control of the current down to a single electron per pulse. In addition, it is extremely important that the pulse that triggers the quantum tunneling of the charges is far from any resonant optical excitation. For these reasons, we will develop a phase-locked Er:fiber laser source equipped with Tm: and Yb:fiber amplifying stages that will be able to generate single optical cycle optical pulses at wavelenghts around 2 microns.We envision that the study of the ultrafast quantum charge transport on samples positioned in the nano-junction will open new exciting parameter ranges and phenomena related to charge transport in quantum systems.