0000000000215212
AUTHOR
Klaus Pierz
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…
Generation of energy selective excitations in quantum hall edge states
We operate an on-demand source of single electrons in high perpendicular magnetic fields up to 30T, corresponding to a filling factor below 1/3. The device extracts and emits single charges at a tunable energy from and to a two-dimensional electron gas, brought into well defined integer and fractional quantum Hall (QH) states. It can therefore be used for sensitive electrical transport studies, e.g. of excitations and relaxation processes in QH edge states.
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.
Robust single-parameter quantized charge pumping
This paper investigates a scheme for quantized charge pumping based on single-parameter modulation. The device was realized in an AlGaAs-GaAs gated nanowire. We find a remarkable robustness of the quantized regime against variations in the driving signal, which increases with applied rf power. This feature together with its simple configuration makes this device a potential module for a scalable source of quantized current.
Single-parameter quantized charge pumping in high magnetic fields
We study single-parameter quantized charge pumping via a semiconductor quantum dot in high magnetic fields. The quantum dot is defined between two top gates in an AlGaAs/GaAs heterostructure. Application of an oscillating voltage to one of the gates leads to pumped current plateaus in the gate characteristic, corresponding to controlled transfer of integer multiples of electrons per cycle. In a perpendicular-to-plane magnetic field the plateaus become more pronounced indicating an improved current quantization. Current quantization is sustained up to magnetic fields where full spin polarization of the device can be expected.
Magnetic field enhanced robustness of quantized current plateaus in single and double quantum dot non-adiabatic single charge pumps
We compare the robustness of the quantized current plateaus of semiconductor non-adiabatic quantized charge pumps consisting of a single quantum dot (SQD) and two QDs connected in series (DQD). For the SQD application of a perpendicular magnetic field leads to an enhanced robustness of the first current plateau I = ef, with f the pumping frequency and e the elementary charge. In contrast for the DQD a comparably enhanced robustness of the plateau I = 2ef is found. These findings might allow generation of higher currents without compromising quantization accuracy by optimizing the device geometry.
Non-adiabatic pumping of single electrons affected by magnetic fields
Non-adiabatic pumping of discrete charges, realized by a dynamical quantum dot in an AlGaAs/GaAs heterostructure, is studied under influence of a perpendicular magnetic field. Application of an oscillating voltage in the GHz-range to one of two top gates, crossing a narrow wire and confining a quantum dot, leads to quantized pumped current plateaus in the gate characteristics. The regime of pumping one single electron is traced back to the diverse tunneling processes into and out-of the dot. Extending the theory to multiple electrons allows to investigate conveniently the pumping characteristics in an applied magnetic field. In this way, a qualitatively different behavior between pumping ev…
Realization of a robust single-parameter quantized charge pump
This paper describes a novel scheme for quantized charge pumping based on single-parameter modulation. The device is realized in an AlGaAs-GaAs gated nanowire. A particular advantage of this realization is that operation in the quantized regime can be achieved in a potentially large range of amplitude and dc off-set of the driving signal. This feature together with the simple configuration might enable large scale parallel operation of many such devices.
Counting statistics for electron capture in a dynamic quantum dot
We report non-invasive single-charge detection of the full probability distribution $P_n$ of the initialization of a quantum dot with $n$ electrons for rapid decoupling from an electron reservoir. We analyze the data in the context of a model for sequential tunneling pinch-off, which has generic solutions corresponding to two opposing mechanisms. One limit considers sequential "freeze out" of an adiabatically evolving grand canonical distribution, the other one is an athermal limit equivalent to the solution of a generalized decay cascade model. We identify the athermal capturing mechanism in our sample, testifying to the high precision of our combined theoretical and experimental methods. …