SCL Seminar by Marko Rancic

On October 10, 2014, at 14:00, in the library of the Institute of Physics Belgrade, Marko Rančić (Department of Physics, University of Konstanz, Germany)  presents a seminar talk entitled:

"Overcoming nuclear-spin-induced decoherence of the electron spin qubit"


The two-electron double quantum dot is a system that is considered to be a good candidate for an electron spin qubit. However, non-zero nuclear spins of the host materials (GaAs, Si, etc.) strongly contribute to the electron spin decoherence. Developing techniques for overcoming nuclear spin induced decoherence is an active field of research. In materials having stable zero nuclear spin isotopes one possible solution is isotopic purification. On the other hand, materials like GaAs and InAs do not have stable zero nuclear spin isotopes, and therefore the nuclear spins must be dynamically polarized (DNP) or dynamically decoupled. In this talk we will give a detailed overview of methods developed to overcome the nuclear-spin-induced decoherence of the two-electron double quantum dot system (DQD), with a special emphasis on our recent results.

In our recent study we explore the interplay of spin-orbit and hyperfine effects on the nuclear preparation schemes in two-electron DQDs in InGaAs.The quantity of utmost interest is the electron spin decoherence time in dependence of the number of sweeps through the electron spin singlet-triplet anti-crossing. Decoherence of the electron spin is caused by the difference field induced by the nuclear spins. We study the case where a singlet S(2,0) is initialized, in which both electrons are in the left dot. Subsequently,the system is driven repeatedly through the anti-crossing and back using linear electrical bias sweeps. In the second part of the talk, we will give an overview of dynamical decoupling methods, with a special emphasis on recent dynamical decoupling experiments conducted in GaAs DQDs in the Yacobi group at Harvard. Further on, we will present our preliminary theoretical studies on dynamical decoupling in two-dimensional materials (e.g. graphene, silicene, etc.). Our results suggest that dynamical decoupling could be made even more efficient in two-dimensional and quasi-two-dimensional materials, as compared to three dimensional materials. This could also give rise to new, more efficient NMR techniques for investigating these types of materials.