Quantum dots are nanoscale structures creating a potential minimum that can be used to trap charged particles.  In our group, we investigate self-assembled InGaAs quantum dots which are embedded in the intrinsic region of a Schottky photodiode to make them electrically tunable. Over the last years, techniques for controlled optical charging and readout of single dots have been developed. In these approaches, excitons are created via laser light and either the electron or hole is extracted by biasing the diode, tuning it to flatband condition. The resulting charged state of the quantum dot is long-lived and can be read out via phololuminesence. Photoluminesence experiments with circularly-polarized light have shown that also the spin state of the electron or the hole trapped in the quantum dot has a long lifetime, exceeding several 100 microseconds at low temperatures.

To further investigate the properties and dynamics of the spin in the quantum dot, coherent spin control is needed during the storage time. For this purpose, a new sample structure with an on-chip Coplanar Stripline Antenna design is developed to provide a microwave field. Using this setup, time-resolved measurements shall be carried out using pulsed microwave irradiation to perform echo experiments, in particular to investigate the decoherence time of the electron or hole spin.

Funding: DFG via SFB 631 “Solid-State Quantum Information Processing”, Teilprojekt C6 “Coherent Control of Electron and Hole Spin Qubits in Quantum Dots and Molecules Using Microwave Fields”

Publications

Proc. SPIE 8272, 827211 (2012)