A5091515874- Quantum and electron transport phenomena
- Advancements in Semiconductor Devices and Circuit Design
- Semiconductor Quantum Structures and Devices
- Semiconductor materials and devices
- Quantum Information and Cryptography
- Nanowire Synthesis and Applications
- Photonic and Optical Devices
- Quantum Computing Algorithms and Architecture
- Force Microscopy Techniques and Applications
- Integrated Circuits and Semiconductor Failure Analysis
- Quantum-Dot Cellular Automata
- Surface and Thin Film Phenomena
- Silicon Nanostructures and Photoluminescence
- Thermal properties of materials
- Molecular Junctions and Nanostructures
- Mechanical and Optical Resonators
- Advanced MEMS and NEMS Technologies
- Semiconductor materials and interfaces
- Carbon Nanotubes in Composites
- Physics of Superconductivity and Magnetism
- Electron and X-Ray Spectroscopy Techniques
- Graphene research and applications
- Advanced Electron Microscopy Techniques and Applications
- Near-Field Optical Microscopy
- Nanofabrication and Lithography Techniques
University of Wisconsin–Madison
2016-2025
UNSW Sydney
2023
Intel (United States)
2018
Delft University of Technology
2017-2018
QuTech
2018
Wisconsin Institutes for Discovery
2017
Dartmouth College
2012
Madison Group (United States)
2008-2012
This review describes recent groundbreaking results in Si, $\mathrm{Si}/\mathrm{SiGe}$, and dopant-based quantum dots, it highlights the remarkable advances Si-based physics that have occurred past few years. progress has been possible thanks to materials development of Si devices, physical understanding effects silicon. Recent critical steps include isolation single electrons, observation spin blockade, single-shot readout individual electron spins both dopants gated dots Si. Each these...
We propose a quantum dot qubit architecture that has an attractive combination of speed and fabrication simplicity. It consists double with one electron in two electrons the other. The itself is set states total spin numbers ${S}^{2}=3/4$ ($S=1/2$) ${S}_{z}=\ensuremath{-}1/2$, different being singlet triplet doubly occupied dot. Gate operations can be implemented electrically highly tunable, enabling fast implementation one- two-qubit gates simpler geometry fewer than other proposed...
Spins based in silicon provide one of the most promising architectures for quantum computing. Quantum dots are an inherently scalable technology. Here, we combine these two concepts into a workable design silicon-germanium bit. The novel structure incorporates vertical and lateral tunneling, provides controlled coupling between dots, enables single electron occupation each dot. Precise modeling elucidates its potential For first time it is possible to translate requirements fault-tolerant...
The qubit is the fundamental building block of a quantum computer. We fabricate in silicon double-quantum dot with an integrated micromagnet which basis states are singlet state and spin-zero triplet two electrons. Because micromagnet, magnetic field difference ΔB between sides double large enough to enable achievement coherent rotation qubit's Bloch vector around different axes sphere. By measuring decay oscillations, inhomogeneous spin coherence time T2* determined. at many values exchange...
The excitation of a high density carriers in semiconductors can induce an order-to-disorder phase transition due to changes the potential-energy landscape lattice. We report first direct resolution structural details this phenomenon freestanding films polycrystalline and (001)-oriented crystalline Si, using 200-fs electron pulses. At levels greater than $\ensuremath{\sim}6%$ valence density, structure lattice is lost $<500\text{ }\text{ }\mathrm{fs}$, time scale indicative electronically...
We demonstrate an optically active nanotube-hybrid material by functionalizing single-wall nanotubes with azo-based chromophore. Upon UV illumination, the conjugated chromophore undergoes a cis-trans isomerization leading to charge redistribution near nanotube. This changes local electrostatic environment, shifting threshold voltage and increasing conductivity of nanotube transistor. For $\ensuremath{\sim}1%--2%$ coverage, we measure shift in up 1.2 V. Further, conductance change is...
We demonstrate single-shot readout of a silicon quantum dot spin qubit, and we measure the relaxation time T1. show that rate loading can be tuned by an order magnitude changing amplitude pulsed-gate voltage, fraction spin-up electrons loaded also controlled. This tunability arises because electron spins through orbital excited state. Using theory includes states energy-dependent tunneling, find global fit to is in good agreement with data.
The gate fidelity and the coherence time of a qubit are important benchmarks for quantum computation. We construct using single electron spin in Si/SiGe dot control it electrically via an artificial spin-orbit field from micromagnet. measure average single-qubit $\approx$ 99$\%$ randomized benchmarking, which is consistent with dephasing slowly evolving nuclear spins substrate. measured dynamical decoupling extends up to 400 $\mu$s 128 pulses, no sign saturation. find evidence that limited...
Arrays of electrically and magnetically controllable electron-spin qubits can be lithographically fabricated on silicon wafers.
Fast quantum oscillations of a charge qubit in double dot fabricated Si/SiGe heterostructure are demonstrated and characterized experimentally. The measured inhomogeneous dephasing time ${T}_{2}^{*}$ ranges from 127 ps to 2.1 ns; it depends substantially on how the energy difference two states varies with external voltages, consistent decoherence process that is dominated by detuning noise (charge changes asymmetry qubit's double-well potential). In regime shortest ${T}_{2}^{*}$, applying...
Isolated spins in semiconductors provide a promising platform to explore quantum mechanical coherence and develop engineered systems. Silicon has attracted great interest as host material for developing spin qubits because of its weak spin-orbit coupling hyperfine interaction, several architectures based on gate defined dots have been proposed demonstrated experimentally. Recently, dot hybrid qubit formed by three electrons double was proposed, non-adiabatic pulsed-gate operation implemented...
Quantum simulators are a promising technology on the spectrum of quantum devices from specialized experiments to universal computers. These utilize entanglement and many-particle behavior explore solve hard scientific, engineering, computational problems. Rapid development over last two decades has produced more than 300 in operation worldwide using wide variety experimental platforms. Recent advances several physical architectures promise golden age ranging highly optimized special purpose...
Abstract Large-scale arrays of quantum-dot spin qubits in Si/SiGe quantum wells require large or tunable energy splittings the valley states associated with degenerate conduction band minima. Existing proposals to deterministically enhance splitting rely on sharp interfaces modifications well barriers that can be difficult grow. Here, we propose and demonstrate a new heterostructure, “Wiggle Well”, whose key feature is Ge concentration oscillations inside well. Experimentally, show placing...
Silicon/silicon-germanium heterostructures have many important advantages for hosting spin qubits. However, controlling the valley splitting (the energy between two low-lying conduction-band valleys) remains a critical challenge ensuring qubit reliability. Broad distributions of splittings are commonplace, even among quantum dots formed on same chip. In this work, we theoretically explore interplay quantum-well imperfections that suppress and cause variability, such as broadened interfaces...