A5031155725- Semiconductor Quantum Structures and Devices
- Quantum and electron transport phenomena
- Quantum Information and Cryptography
- Advancements in Semiconductor Devices and Circuit Design
- Semiconductor materials and devices
- Quantum Dots Synthesis And Properties
- Neural Networks and Reservoir Computing
- Photonic Crystals and Applications
- Molecular Junctions and Nanostructures
- Photonic and Optical Devices
- Semiconductor Lasers and Optical Devices
- Magnetic properties of thin films
- Quantum optics and atomic interactions
- Surface and Thin Film Phenomena
- Quantum Computing Algorithms and Architecture
- Electronic and Structural Properties of Oxides
- Mechanical and Optical Resonators
- Magnetic Field Sensors Techniques
- Advanced Chemical Physics Studies
- Diamond and Carbon-based Materials Research
- Advanced Semiconductor Detectors and Materials
- Near-Field Optical Microscopy
- Nanowire Synthesis and Applications
- Graphene research and applications
- Optical Network Technologies
Ruhr University Bochum
2015-2024
Quantum dots are both excellent single-photon sources and hosts for single spins. This combination enables the deterministic generation of Raman-photons -- bandwidth-matched to an atomic quantum-memory photon cluster states, a resource in quantum communication measurement-based computing. GaAs AlGaAs can be matched frequency rubidium-based memory, have potentially improved electron spin coherence compared widely used InGaAs dots. However, their charge stability optical linewidths typically...
A spin-photon interface should operate with both coherent photons and a spin to enable cluster-state generation entanglement distribution. In high-quality devices, self-assembled GaAs quantum dots are near-perfect emitters of on-demand photons. However, the rapidly decoheres via magnetic noise arising from host nuclei. Here, we address this drawback by implementing an all-optical nuclear-spin cooling scheme on dot. The electron-spin coherence time increases 156-fold ${T}_{2}^{*}=3.9\text{...
The Stranski-Krastanov (SK) growth-mode facilitates the self-assembly of quantum dots (QDs) using lattice-mismatched semiconductors, for instance InAs and GaAs. SK QDs are defect-free can be embedded in heterostructures nano-engineered devices. excellent photon emitters: QD-excitons, electron-hole bound pairs, exploited as emitters high quality single photons communication. One significant drawback SK-mode is wetting layer (WL). WL results a continuum rather close energy to...
Semiconductor spin qubits have recently seen major advances in coherence time and control fidelities, leading to a single-qubit performance that is on par with other qubit platforms. Most of this progress based microwave single spins devices made isotopically purified silicon. For controlling spins, the exchange interaction an additional key ingredient which poses new challenges for high-fidelity control. Here, we demonstrate exchange-based gates two-electron GaAs double quantum dots. Using...
A crucial requirement for quantum computing---in particular, scalable computing and error correction---is fast high-fidelity qubit readout. For semiconductor-based qubits, one limiting factor local low-power signal amplification is the output swing of charge sensor. We demonstrate $\mathrm{Ga}\mathrm{As}$ Si asymmetric sensing dots (ASDs) specifically designed to provide a significantly larger response compared conventional charge-sensing dots. Our ASD design features drain reservoir...
Precise control of the properties semiconductor quantum dots (QDs) is vital for creating novel devices photonics and advanced opto-electronics. Suitable low QD-densities single QD experiments are challenging to during epitaxy typically found only in limited regions wafer. Here, we demonstrate how conventional molecular beam (MBE) can be used modulate density optically active QDs one- two- dimensional patterns, while still retaining excellent quality. We find that material thickness gradients...
Quantum networking technologies use spin qubits and their interface to single photons as core components of a network node. This necessitates the ability co-design magnetic- optical-dipole response quantum system. These properties are notoriously difficult design in many solid-state systems, where spin-orbit coupling crystalline environment for each qubit create inhomogeneity electronic g-factors optically active states. Here, we show that GaAs dots (QDs) obtained via quasi-strain-free local...
We present near-unity two-photon interference visibilities for single-photon states generated from two separate GaAs quantum dots. This level of visibility is the first its kind among solid-state emitters and matches performance pure platforms such as atoms ions.
A semiconductor quantum dot (QD) can generate highly indistinguishable single photons at a high rate. For application in communication and integration hybrid systems, control of the QD optical properties is essential. Understanding connection between growth process therefore important. Here, we show for GaAs QDs, grown by infilling droplet-etched nanoholes, that emission wavelength, neutral-to-charged exciton splitting, diamagnetic shift are strongly correlated with capture-zone area, an...
Decoherence of a quantum system arising from its interaction with an environment is key concept for understanding the transition between and classical world as well performance limitations in technology applications. The effects large, weakly coupled environments are often described classical, fluctuating field whose dynamics unaffected by qubit, whereas fully description still implies some backaction qubit on environment. Here we show direct experimental evidence such electron-spin GaAs dot...
Combining the capabilities of gate-defined quantum transport devices in $\mathrm{Ga}\mathrm{As}$-based heterostructures and optically addressed self-assembled dots could open up broad perspectives technologies. For example, interfacing stationary solid-state qubits with photonic states would a pathway towards realization network extended processing capacity each node. While gated allow very flexible confinement electrons or holes, excitons without some element self-assembly is much harder....
Scaling up a quantum processor to tackle real-world problems requires qubit numbers in the millions. Scalable semiconductor-based architectures have been proposed, many of them relying on integrated control instead room-temperature electronics. However, it has not yet shown that this can be achieved. For developing high-density, low-cost wiring solution, is highly advantageous for electronics placed at same temperature as chip. Therefore, tight integration chip with ultra low power...
Gate layouts of spin-qubit devices are commonly adapted from previous successful devices. As qubit numbers and device complexity increase, modeling new optimizing for yield performance become necessary. The simulation tools used in the advanced semiconductor industry need to be smaller structure sizes electron numbers. Here, we present a general approach electrostatically spin-qubit-device layouts, considering gate voltages, heterostructures, doping, reservoirs, an applied source-drain bias....
Accumulation mode devices with epitaxially grown gates have excellent electrical stability due to the absence of dopant impurities and surface states. We overcome typical fabrication issues associated gated structures (e.g., gate leakage high contact resistance) by using separate control electron densities in Ohmic Hall bar regions. This hybrid architecture opens up a way make ultrastable nanoscale where separation between 2D gas is small. In this work, we demonstrate that made from same...
In this submission, we discuss the growth of charge-controllable GaAs quantum dots embedded in an n-i-p diode structure, from perspective a molecular beam epitaxy grower. The QDs show no blinking and narrow linewidths. We that parameters used led to bimodal mode resulting low arsenic surface coverage. identify one modes as showing good properties found previous work. As morphology fabricated does not hint at outstanding properties, attribute performance sample impurity levels matrix material...
Abstract In a radiative Auger process, optical decay leaves other carriers in excited states, resulting weak red-shifted satellite peaks the emission spectrum. The appearance of directly leads to question if process can be inverted: simultaneous photon absorption and electronic demotion. However, excitation transition has not been shown, neither on atoms nor solid-state quantum emitters. Here, we demonstrate driving transition, linking few-body Coulomb interactions optics. We perform our...
Among various solid-state systems, gate-defined quantum dots (QD) with high scalability and controllability for single electron spin qubits are promising candidates to realize spin-photon interface. The efficiency of the interface is expected be significantly enhanced by optical coupling QDs photonic crystal (PhC) nanocavities. As first step towards this coupling, we designed experimentally demonstrated a PhC nanocavity electrodes. electrodes, which can form QD, were introduced on top...
Abstract Electron spins in gate-defined quantum dots (QDs) formed semiconductor wells (QWs) are promising stationary qubits for implementing large-scale networks a scalable manner. One key ingredient such network is an efficient photon–spin interface that converts any polarization state of flying photonic qubit to the corresponding electron QDs. A bull’s-eye cavity optical structure can enhance photon absorption embedded QD without dependence. In this paper, we report successful fabrication...
Persistent photoconductivity of GaAs/AlGaAs heterostructures has hampered the measurement charge- and spin-related quantum effects in gate-defined devices integrated charge sensors due to Si-dopant-related deep donor levels (DX centers). In this study, effect is overcome by using an undoped heterostructure for photonic purposes. We also measure electron transport before after LED illumination at low temperatures. addition a regular rapid saturation showing increased carrier density, slow...
Abstract The electron mobility in shallow GaAs/Al x Ga 1−x As heterostructures is strongly suppressed by charge wafer surface, which arises from native surface oxide layers formed when the removed crystal growth system. Here an situ epitaxial aluminum gate, grown as part of wafer, used to eliminate scattering. Transmission microscope characterization shows that crystalline, and free oxide. influence Al thickness use different semiconductor wetting at semiconductor‐aluminum interface are...
Gate-layouts of spin qubit devices are commonly adapted from previous successful devices. As numbers and the device complexity increase, modelling new layouts optimizing for yield performance becomes necessary. Simulation tools advanced semiconductor industry need to be smaller structure sizes electron numbers. Here, we present a general approach electrostatically layouts, considering gate voltages, heterostructures, reservoirs an applied source-drain bias. Exemplified by specific potential,...