Coherent devices based on semiconductor quantum dots
We are investigating the potential to perform conditional quantum logic operations using solid-state hardware in the basis of charge and spin excitations in individual quantum dots and electronically coupled quantum dot molecules. In particular, the spin of single electrons in such zero dimensional nanostructures represents one of the most promising routes towards the realisation of a quantum bit (qubit), the fundamental logical unit in future quantum computers. In order to be able to perform reliable quantum operations, the spin must interact only weakly with its environment in order to maintain phase coherence. Whilst in bulk semiconductors the spin lifetime tends to be short, it is found to be much longer in quantum dots due to their discrete electronic structure. Another area of our research is focussed on the potential to optically initialise and readout the state of such spin qubits using a "spin memory" device as depicted schematically in the figure. Such device architectures may provide a stepping stone towards the realisation of quantum spin-chips based on arrays of electronically coupled quantum dot nanostructures. This work is supported financially by DFG via SFB 631.
