Promotionsprogramm hsnForschungsprojekte
Quantum Dots as Spin-Qubits and Spin-Photon-Interfaces

Quantum Dots as Spin-Qubits and Spin-Photon-Interfaces

Leitung:  Supervisor: Prof. Dr. Michael Oestreich, LUH, Institute of Solid State Physics. Co-Supervisor: Prof. Dr. Fei Ding, LUH, Institute of Solid State Physics
Jahr:  2020
Bemerkungen:  Projekt-ID:86

Semiconductor quantum dots are excellent candidates for optically addressable spin qubits. Single carriers localized in such quantum dots exhibit not only promising phase coherence times but additionally very long spin decoherence times which enables the potential efficient storage and manipulation of quantum information.

Recent experiments from our group show the intriguing spin dynamics of such single carriers in (InGa)As/GaAs quantum dots and their interaction with the local environment.1,2 In this PhD project we will focus on the spin dynamics (a) of quantum dots emitting photons at telecommunication wavelengths at 1.55µm (C-band) and (b) of unstrained quantum dots. The spin dynamics of such quantum dots is most important in view of fiber-based spin-photon interfaces since the C-band is used as standard for today’s long distance optical data communication because of the extremely low light absorption. Up to now, this kind of quantum dots exhibit significant internal strain which inter alia limits the spin state decoherence time in comparison to unstrained quantum dots.

Therefore, we study in close collaboration with the group of Prof. Dr. Fei Ding a new kind of quantum dots, which are grown by nano-droplet epitaxy and do not exhibit any significant internal strain. These “strain free” quantum dots can be easily manipulated by external strain and are thereby perfect candidates to study the influence of strain on the spin dynamics. The collaboration with Prof. Dr. Fei Ding allows at the same time to measure the influence of the spin dephasing time on the phase coherence time which is currently the most important parameter in view of solid state optical quantum links.

[1] Wiegand et al., “Spin and reoccupation noise beyond the fluctuation-dissipation theorem”, PRB 97, 081403(R) (2018).
[2] Wiegand et al., “Hole-capture competition between a single quantum dot and an ionized acceptor”, PRB 98, 125426 (2018).