Fast flux control of 3D transmon qubits using a magnetic hose

Fast magnetic flux control is a crucial ingredient for circuit quantum electrodynamics (cQED) systems. So far it has been a challenge to implement this technology with the high coherence 3D cQED architecture. In this paper we control the magnetic field inside a superconducting waveguide cavity using a magnetic hose, which allows fast flux control of 3D transmon qubits on time scales < 100 ns. The hose is designed as an effective microwave filter to not compromise the energy relaxation time of the qubit. The magnetic hose is a promising tool for fast magnetic flux control in various platforms intended for quantum information processing and quantum optics.Comment: 9 pages, 7 figures, including supplementary materia

How Abundant is Pedogenic Magnetite? Abundance and Grain Size Estimates for Loessic Soils Based on Rock Magnetic Analyses

The upper soil horizons of many modern and ancient soils are enriched in fine-grained pedogenic ferrimagnetic minerals. We use three grain-size- and concentration-dependent proxies (anhysteretic remanent magnetization/isothermal remanent magnetization ratios, coercivity spectra derived from alternating field demagnetization of saturation isothermal remanent magnetization and hysteresis properties) to quantify the abundance and grain size of the pedogenic magnetic component. Our analyses of modern loessic soils from the midwestern United States show that relatively small additions (2–10 vol % of the total ferrimagnetic component) of fine-grained (coarse superparamagnetic to fine pseudosingle domain) magnetite or maghemite are sufficient to explain the changes in concentration and grain-size-dependent properties observed in the upper soil horizons. Furthermore, the pedogenic components of all studied sites display a narrow range of magnetic properties, which argues for a common origin of these particles over a wide range of climatic conditions

A Task-based Knowledge Management Case for Addressing Merger and Acquisition Risk

For some firms, mergers and acquisitions (M&A) activity is part of a normal growth strategy in a competitive environment. Such firms accumulate a body of M&A knowledge that can be employed for the benefits of organisational continuity. Despite the significant risks associated with M&A failure, they are able to approach each new event with a set of experiential learnings that can better inform their actions. For other firms however, M&A represent rare occasions in the company’s lifecycle. Valuable integration knowledge is inherently fragmented, making these firms especially vulnerable to M&A risks. A case study was undertaken in a firm that matches this latter category. A Task-based Knowledge Management approach provided a framework for inquiry. Our focus was on knowledge work associated with the post-acquisition integration task of an acquirer. The findings reveal substantial M&A learnings, which if harnessed adequately, can enhance firm’s competitive advantage and mitigate against associated M&A risk

Mechanisms of endocytosis and exocytosis in rat gastric enterochromaffin-like (ECL) cells

Enterochromaffin-like (ECL) Zellen sind neuroendokrine Zellen der Magenschleimhaut, die eine wichtige Rolle bei der peripheren Regulation der Magensäureproduktion spielen. Nach Stimulation mit Gastrin kommt es zur calciumabhängigen Freisetzung von Histamin, das in Parietalzellen die Synthese und Sekretion von Magensäure auslöst. In vorliegender Arbeit wurden Bedeutung und Entstehung des Calciumsignals für die gastrininduzierte Histaminsekretion sowie Expression der Endozytoseproteine Amphiphysin und Dynamin untersucht. Für die Erhöhung von [Ca2+]i war die Aktivierung von InsP3-Rezeptoren, nicht jedoch die Entleerung intrazellulärer Calciumspeicher nötig. Der für die Exozytose notwendige Calciumeinstrom konnte durch Nimodipin gehemmt werden, was eine Beteilung spannungsgesteuerter L-Typ Calciumkanäle nahe legt. Alle Dynamin- und Amphiphysin-Isoformen konnten auf mRNA- und Proteinebene nachgewiesen werden. Eine neue Splice-Variante von Amphiphysin-2 wurde ebenfalls entdeckt.Enterochromaffin-like (ECL) cells are neuroendocrine cells of the gastric mucosa that are important for the peripheral regulation of gastric acid secretion. Following stimulation with gastrin, histamine is released from ECL cells in a calcium-dependent manner, inducing synthesis and secretion of gastric acid in parietal cells. In this thesis, importance and generation of the calcium signal necessary for gastrin-induced histamine secretion were investigated, as well as the expression of the endocytic proteins amphiphysin and dynamin. Activation of InsP3 receports but not calcium release from intracellular stores was nessecary for the increase in [Ca2+]i. Calcium influx could be inhibited by nimodipine, indicating involvement of voltage-activated L-type calcium channels. All known dynamin and amphiphysin isoforms could be detected on mRNA and protein levels. Furthermore, a novel splice form of amphiphysin-2 was found to be expressed in ECL cells

Root and Vigor Response of Big Bluestem to Summer Grazing Strategies

Warm-season grasses e.g., big bluestem (Andropogon gerardii Vitman) are great potential sources of summer forage in eastern Nebraska. Frequent, intensive defoliation can reduce root mass and limit root distribution. Quantifying root structure response to multiple defoliation events in a grazing situation is critical to develop management plans for these types of grasses. This experiment aimed to quantify the cumulative effects of timing and frequency of grazing on root structure and organic reserve estimates in big bluestem pastures

Visualizing the emission of a single photon with frequency and time resolved spectroscopy

At the dawn of Quantum Physics, Wigner and Weisskopf obtained a full analytical description (a \textit{photon portrait}) of the emission of a single photon by a two-level system, using the basis of frequency modes (Weisskopf and Wigner, "Zeitschrift f\"ur Physik", 63, 1930). A direct experimental reconstruction of this portrait demands an accurate measurement of a time resolved fluorescence spectrum, with high sensitivity to the off-resonant frequencies and ultrafast dynamics describing the photon creation. In this work we demonstrate such an experimental technique in a superconducting waveguide Quantum Electrodynamics (wQED) platform, using single transmon qubit and two coupled transmon qubits as quantum emitters. In both scenarios, the photon portraits agree quantitatively with the predictions of the input-output theory and qualitatively with Wigner-Weisskopf theory. We believe that our technique allows not only for interesting visualization of fundamental principles, but may serve as a tool, e.g. to realize multi-dimensional spectroscopy in waveguide Quantum Electrodynamics.Comment: 18 pages, 10 figures including appendice

Nonreciprocity realized with quantum nonlinearity

Nonreciprocal devices are a key element for signal routing and noise isolation. Rapid development of quantum technologies has boosted the demand for a new generation of miniaturized and low-loss nonreciprocal components. Here we use a pair of tunable superconducting artificial atoms in a 1D waveguide to experimentally realize a minimal passive nonreciprocal device. Taking advantage of the quantum nonlinear behavior of artificial atoms, we achieve nonreciprocal transmission through the waveguide in a wide range of powers. Our results are consistent with theoretical modeling showing that nonreciprocity is associated with the population of the two-qubit nonlocal entangled quasi-dark state, which responds asymmetrically to incident fields from opposing directions. Our experiment highlights the role of quantum correlations in enabling nonreciprocal behavior and opens a path to building passive quantum nonreciprocal devices without magnetic fields

Spatial Addressing of Qubits in a Dispersive Waveguide

Waveguide quantum electrodynamics, the study of atomic systems interacting with propagating electromagnetic fields, is a powerful platform for understanding the complex interplay between light and matter. Qubit control is an indispensable tool in this field, and most experiments have so far focused on narrowband electromagnetic waves that interact with qubits at specific frequencies. This interaction, however, changes significantly with fast, broadband pulses, as waveguide properties like dispersion affect the pulse evolution and its impact on the qubit. Here, we use dispersion to achieve spatial addressing of superconducting qubits separated by a sub-wavelength distance within a microwave waveguide. This novel approach relies on a self-focusing effect to create a position-dependent interaction between the pulse and the qubits. This experiment emphasizes the importance of dispersion in the design and analysis of quantum experiments, and offers new avenues for the rapid control of quantum states