Relatore: Fabrizio Moro, Department of Physics, Linkoping University, Sweden.

Abstract:

The controlled incorporation of magnetic dopants in quantum dots (QDs) is a challenging research eld with potential for numerous applications in Nanotechnology, including quantum information processing and energy conversion. Of particular interest is the incorporation of 3d transition metal ions (Mn, Co, etc...) whose d-shell electronic congurations imprint the nanocrystal with functional magnetic and optical properties.
We report on the optical and magnetic properties of Mn ions doped into colloidal PbS QDs. We observe a blue-shift of the photoluminescence (PL) and a decrease of the exciton g-factor upon increasing the Mn content, thus suggesting tunability of the dopant-carrier s,p-d exchange interaction.
For singly doped QDs, electron spin resonance (ESR) studies reveal the six hyperne lines of isolated 55Mn2+ ions. Long phase memory times (TM 10 s at 5 K) up to near room temperature (TM 1 s at 260K) were detected by pulsed-ESR methods after minimization of the major sources of decoherence. Finally, we use electron double resonance methods to detect the full Mn2+ NMR spectrum and to drive Rabi oscillations implementing NOT and SWAP universal quantum gates.
In conclusion, Mn2+ ions provide a means for tuning the optical and magnetic properties of QDs and represent a multi-level quantum bit system, i.e. a qudit, beyond traditional spin-qubits in QDs, for quantum computing application, whose states can be detected, coherently manipulated and potentially optically read-out via the sp-d interaction.