0000000000215214
AUTHOR
Rolf J. Haug
Partitioning of on-demand electron pairs
The on-demand generation and separation of entangled photon pairs are key components of quantum information processing in quantum optics. In an electronic analogue, the decomposition of electron pairs represents an essential building block for using the quantum state of ballistic electrons in electron quantum optics. The scattering of electrons has been used to probe the particle statistics of stochastic sources in Hanbury Brown and Twiss experiments and the recent advent of on-demand sources further offers the possibility to achieve indistinguishability between multiple sources in Hong-Ou-Mandel experiments. Cooper pairs impinging stochastically at a mesoscopic beamsplitter have been succe…
Quantized current source with mesoscopic feedback
We study a mesoscopic circuit of two quantized current sources, realized by nonadiabatic single-electron pumps connected in series with a small micron-sized island in between. We find that quantum transport through the second pump can be locked onto the quantized current of the first one by a feedback due to charging of the mesoscopic island. This is confirmed by a measurement of the charge variation on the island using a nearby charge detector. Finally, the charge feedback signal clearly evidences loading into excited states of the dynamic quantum dot during single-electron pump operation. © 2011 American Physical Society.
Interaction-induced spin polarization in quantum dots.
The electronic states of lateral many electron quantum dots in high magnetic fields are analyzed in terms of energy and spin. In a regime with two Landau levels in the dot, several Coulomb blockade peaks are measured. A zig-zag pattern is found as it is known from the Fock-Darwin spectrum. However, only data from Landau level 0 show the typical spin-induced bimodality, whereas features from Landau level 1 cannot be explained with the Fock-Darwin picture. Instead, by including the interaction effects within spin-density-functional theory a good agreement between experiment and theory is obtained. The absence of bimodality on Landau level 1 is found to be due to strong spin polarization.
Observation of sequential spin flips in quantum rings
We observe strong signatures of spin flips in quantum rings exposed to external magnetic fields in the Coulomb blockade regime. The signatures appear as a pattern of lines corresponding to local reduction of conductance, and they cover a large range of magnetic fields and number of electrons. The sequence of lines, as well as other features in the conductance, can be captured by many-electron calculations within density-functional theory. The calculations show that most lines in the pattern correspond to sequential spin flips between filling factors 2 and 1. We believe that the ability to probe individual spin flips provides an important step toward precise spin control in quantum ring devi…