A5018297936- Quantum and electron transport phenomena
- Semiconductor Quantum Structures and Devices
- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Condensed Matter Physics
- Magnetic Properties of Alloys
- Quantum Information and Cryptography
- Quantum Computing Algorithms and Architecture
- Magnetic properties of thin films
- Surface and Thin Film Phenomena
- Semiconductor materials and devices
- Rare-earth and actinide compounds
- Quantum Dots Synthesis And Properties
- Multiferroics and related materials
- Neural Networks and Reservoir Computing
- Graphene research and applications
- Topological Materials and Phenomena
- Boron and Carbon Nanomaterials Research
- Silicon Nanostructures and Photoluminescence
- Machine Learning in Materials Science
- Advanced biosensing and bioanalysis techniques
- Phase-change materials and chalcogenides
- Advanced ceramic materials synthesis
- Electronic and Structural Properties of Oxides
Florida State University
2009-2024
IQM (Finland)
2022-2023
University of Maryland, College Park
2019-2022
Physical Sciences (United States)
2019-2022
University of Basel
2018-2021
Tunable coupling of superconducting qubits has been widely studied due to its importance for isolated gate operations in scalable quantum processor architectures. Here, we demonstrate a tunable qubit-qubit coupler based on floating transmon device, which allows us place at least 2 mm apart from each other while maintaining over 50-MHz between the and qubits. In introduced tunable-coupler design, both qubit-coupler couplings are mediated by two waveguides instead relying direct capacitive...
Abstract Scalable quantum technologies such as computers will require very large numbers of devices to be characterised and tuned. As the number on chip increases, this task becomes ever more time-consuming, intractable a scale without efficient automation. We present measurements dot device performed by machine learning algorithm in real time. The selects most informative perform next combining information theory with probabilistic deep-generative model that can generate full-resolution...
Understanding and control of the spin relaxation time T1 is among key challenges for spin-based qubits. A larger generally favored, setting fundamental upper limit to qubit coherence readout fidelity. In GaAs quantum dots at low temperatures high in-plane magnetic fields B, relies on phonon emission spin-orbit coupling. The characteristic dependence ∝ B-5 pronounced B-field anisotropy were already confirmed experimentally. However, it has also been predicted 15 years ago that enough fields,...
Abstract Deep reinforcement learning is an emerging machine-learning approach that can teach a computer to learn from their actions and rewards similar the way humans experience. It offers many advantages in automating decision processes navigate large parameter spaces. This paper proposes efficient measurement of quantum devices based on deep learning. We focus double dot devices, demonstrating fully automatic identification specific transport features called bias triangles. Measurements...
Magnetic measurements under high-pressure conditions are pivotal for the study of superconductivity and magnetic materials but remain challenging due to micrometer-sized sample in diamond anvil cells (DAC). In this study, we propose a quantum sensing approach utilizing negatively charged boron-vacancy (V$_B^-$) spin defects two-dimensional hexagonal boron nitride high resolution pressure. The optical properties VB$^-$ were systematically studied conditions, revealing significant...
Device variability is a bottleneck for the scalability of semiconductor quantum devices. Increasing device control comes at cost large parameter space that has to be explored in order find optimal operating conditions. We demonstrate statistical tuning algorithm navigates this entire space, using just few modelling assumptions, search specific electron transport features. focused on gate-defined dot devices, demonstrating fully automated two different devices double regimes an up...
This work reports a study of the nonlinear Hall effect (HE) in semimetallic ferromagnet EuB(6). A distinct switch its resistivity slope is observed paramagnetic phase, which occurs at single critical magnetization over wide temperature range. The observation interpreted as point percolation for entities more conducting and magnetically ordered phase less background. With an increasing applied magnetic field, regions either increase number or expand beyond limit, hence global conductivity...
Fault-tolerant spin-based quantum computers will require fast and accurate qubit readout. This can be achieved using radio-frequency reflectometry given sufficient sensitivity to the change in capacitance associated with states. Here, we demonstrate a 23-fold improvement by supplementing cryogenic semiconductor amplifier SQUID preamplifier. The operates at frequency near 200 MHz achieves noise temperature below 600 mK when integrated into circuit, which is within factor 120 of limit. It...
Quantum two-level systems (TLSs) are present in the materials of qubits and considered defects because they limit qubit coherence. For superconducting qubits, quintessential Josephson junction barrier is made amorphous alumina, which hosts TLSs. However, TLSs not generally understood, either structurally or atomic composition. In this study, we greatly extend quantitative data available on by reporting physical dipole moment two alumina types: polycrystalline...
We show that in-plane-magnetic-field assisted spectroscopy allows extraction of the in-plane orientation and full 3D shape quantum mechanical orbitals a single electron GaAs lateral dot with sub-nm precision. The method is based on measuring orbital energies in magnetic field various strengths orientations plane 2D gas. As result, we deduce microscopic confinement potential landscape, quantify degree by which it differs from harmonic oscillator potential. used to validate manipulation gate...
We theoretically investigate the orbital effects of an in-plane magnetic field on spectrum a quantum dot embedded in two-dimensional electron gas (2DEG). derive effective Hamiltonian where these enter proportion to flux penetrating 2DEG. quantify latter detail for harmonic, triangular, and square potential heterostructure. show how allow one extract wealth information, example, heterostructure interface, size orientation, spin-orbit fields. illustrate formalism by extracting this information...
Abstract Quantum devices with a large number of gate electrodes allow for precise control device parameters. This capability is hard to fully exploit due the complex dependence these parameters on applied voltages. We experimentally demonstrate an algorithm capable fine-tuning several at once. The acquires measurement and assigns it score using variational auto-encoder. Gate voltage settings are set optimize this in real-time unsupervised fashion. report times double quantum dot within...
Despite extensive experimental and theoretical efforts, the important issue of effects surface magnetic impurities on topological state a insulator (TI) remains unresolved. We elucidate Cr epitaxial thin films $({\mathrm{Bi}}_{0.5}{\mathrm{Sb}}_{0.5}{)}_{2}{\mathrm{Te}}_{3}$: adatoms are incrementally deposited onto TI held in ultrahigh vacuum at low temperatures, situ magnetoconductivity Hall effect measurements performed each increment with electrostatic gating. In experimentally...
Quantum two-level systems (TLSs) intrinsic to glasses induce decoherence in many modern quantum devices, such as superconducting qubits. Although the low-temperature physics of these TLSs is usually well-explained by a phenomenological standard tunneling model independent TLSs, nature well their behavior out equilibrium and at high energies above 1 K, remain inconclusive. Here we measure non-equilibrium dielectric loss amorphous silicon using resonator, where are varied time swept electric...
Compared to irreversible gate operations, reversible digital logic gates can provide a fundamental advantage in energy efficiency. Here we discuss previously discovered 1-bit ballistic and new experimental plans measure it. The consist of long Josephson junctions (LJJs) connected by circuit interface. dynamics evanescently extends into the LJJs realize physically resonant operation. It differs from known adiabatic superconducting because it does not work limit. Depending on type, that is...
The electronic phase separation (EPS) of optimally doped ${\mathrm{La}}_{2/3}{\mathrm{Ca}}_{1/3}\mathrm{Mn}{\mathrm{O}}_{3}$ (LCMO) thin films under various degrees anisotropic strain is investigated by static magnetotransport and dynamic relaxation measurements. Three LCMO were grown simultaneously on (001) $\mathrm{NdGa}{\mathrm{O}}_{3}$ substrates pulsed laser deposition, then postgrowth annealed at $780{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$ in ${\mathrm{O}}_{2}$...
Systematic transport measurements have been performed on a series of La0.67Ca0.33MnO3 thin films with varying degrees anisotropic strain. The strain is induced via epitaxial growth NdGaO3(001) substrates and varied by controlling the thermal annealing time. An antiferromagnetic insulating (AFI) state, possibly associated charge ordering, emerges upon annealing. Hall effect in these materials exhibits features that are indicative percolative phase transition correlate closely emergence AFI...
This paper reports on a study of the resistivity and Hall effect ferromagnetic pyrochlore $\mathrm{L}{\mathrm{u}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{7}$. The temperature dependence single crystalline $\mathrm{L}{\mathrm{u}}_{2}{\mathrm{V}}_{2}{\mathrm{O}}_{7}$ exhibits overall activation behavior with metalliclike exception at intermediate temperatures near Curie $({T}_{C})$. bears surprising resemblance to that doped semiconductors. oxide shows negative magnetoresistance (MR) which scales...
Single-Flux Quantum (SFQ) digital logic is typically both energy efficient and fast, but the that uses reversibility provides most extreme method for improving efficiency. We are studying engineered long Josephson junctions (LJJs) components future ballistic gates within a family named Reversible Fluxon Logic (RFL). Therein, bit states represented by two possible polarities of an SFQ. Here we test LJJs with component JJ critical currents 7.5uA penetration depth approximately 2.4 unit cells....
We experimentally determine isotropic and anisotropic $g$-factor corrections in lateral GaAs single-electron quantum dots. extract the Zeeman splitting by measuring tunnel rates into individual spin states of an empty dot for in-plane magnetic field with various strengths directions. quantify energy find a linear dependence on strength that allows us to $g$ factor. The measured factor is understood terms spin-orbit interaction induced bulk Experimental detection identification minute...