Interference and parity blockade in transport through a Majorana box

A Majorana box - two topological superconducting nanowires coupled via a trivial superconductor - is a building block in devices aiming to demonstrate nonabelian physics, as well as for topological quantum computer architectures. We theoretically investigate charge transport through a Majorana box and show that current can be blocked when two Majoranas couple to the same lead, fixing their parity. In direct analogy to Pauli spin blockade in spin qubits, this parity blockade can be used for fast and high-fidelity qubit initialization and readout, as well as for current-based measurements of decoherence times. Furthermore, we demonstrate that transport can distinguish between a clean Majorana box and a disordered box with additional unwanted Majorana or Andreev bound states.Comment: 4 pages, 3 figures + 6 pages supplementar

Classical and Quantum Signatures of Quantum Phase Transitions in a (Pseudo) Relativistic Many-Body System

We identify a (pseudo) relativistic spin-dependent analogue of the celebrated quantum phase transition driven by the formation of a bright soliton in attractive one-dimensional bosonic gases. In this new scenario, due to the simultaneous existence of the linear dispersion and the bosonic nature of the system, special care must be taken with the choice of energy region where the transition takes place. Still, due to a crucial adiabatic separation of scales, and identified through extensive numerical diagonalization, a suitable effective model describing the transition is found. The corresponding mean-field analysis based on this effective model provides accurate predictions for the location of the quantum phase transition when compared against extensive numerical simulations. Furthermore, we numerically investigate the dynamical exponents characterizing the approach from its finite-size precursors to the sharp quantum phase transition in the thermodynamic limit

Theory of non-integer high-harmonic generation in a topological surface state

High harmonic generation is a versatile experimental technique for probing ultrafast electron dynamics. While in the past it has been employed typically in dielectrics and semiconductors, recently high harmonic generation was also observed from a topological surface [Schmid et al., Nature 593, 385 (2021)]. It has been found that harmonic orders in the intermediate range of 13-18 continuously shift when the carrier envelope phase (CEP) is varied. In this work, we adopt a minimal model of the topological surface state and calculate analytically the high-harmonic spectrum. We derive formulae describing the parametric dependencies of CEP shifts in high harmonics; in particular, we have a transparent result for the shift of the (peak) frequency ω when changing the CEP φ: dω/dφ=−2f¯′ω/ω0, where ω0 describes the fundamental driving frequency and f¯′ characterizes the chirp of the driving laser pulse. We compare the analytical formula to full-fledged numerical simulations finding only 17% average absolute deviation in dω/dφ. Our analytical result is fully consistent with experimental observations. It therefore provides the first understanding of the phenomenon of CEP shifts in solids based on analytically derived parametric dependencies

Semiconductor Bloch-equations formalism: Derivation and application to high-harmonic generation from Dirac fermions

We rederive the semiconductor Bloch equations emphasizing the close link to the Berry connection. Our rigorous derivation reveals the existence of two further contributions to the current, in addition to the frequently considered intraband and polarization-related interband terms. The extra contributions become sizable in situations with strong dephasing or when the dipole-matrix elements are strongly wave-number dependent. We apply the formalism to high-harmonic generation for a Dirac metal. The extra terms add to the frequency-dependent emission intensity (high-harmonic spectrum) significantly at certain frequencies changing the total signal up to a factor of 10

Mild cognitive impairment and kidney disease: clinical aspects.

Chronic kidney disease (CKD) is now seen as a systemic disease involving also the central nervous system [1], but the link between the kidney and different organ systems and disease went unnoticed for a long time. The king of Poland, Stephen Bathory (1533-86), suffered from CKD due to polycystic kidney disease and depression [2]. Similarly, Wolfgang Amadeus Mozart was also thought to have had CKD [3] and depression [4]. A list of 'Famous People Who Have Died from Kidney Disease' [5] includes many who suffered from both CKD and depression or other signs of mental illness. Is this a coincidence or actually evidence of a link between kidney disease and brain dysfunction? This is not merely an academic question because all forms of mental illness can seriously impair an individual's quality of life, and are frequently associated with progression of diseases and premature mortality, so it is worth the effort of trying to answer it. Europe and much of the industrialized countries are experiencing growing numbers of patients with CKD within their ageing populations [6]. CKD is complex and potentially fatal: (i) all organs are affected, sooner or later; (ii) the balance of plasma volume, electrolytes, acid-base and minerals, metabolites, hormones and proteins is disturbed; and (iii) patients often need a multidisciplinary team approach managing complex comorbidities, drug regimens and special diets. Although the prognosis of patients with CKD remains poor, their increasing life expectancy has shifted medical attention from life-threatening emergencies to long-term complications and sequelae, and how to improve quality of life [7]. Indeed, kidney failure has detrimental effects on health-related quality of life (HRQoL), reaching levels similar to those seen in patients with metastatic cancer [8]. This might be due to psychological factors, both kidney disease and cancer being chronic diseases with a bad prognosis. However, although the effect of CKD on quality of life is more evident in advanced stages (stage G4P) and in older patients [9, 10], a large study has shown a significant decrease in HRQoL as early as CKD stage G2 [11]. Notably, neurological and cognitive impairments [12], and depression [13] are among the most debilitating consequences of CKD contributing to the significantly reduced HRQoL [14]

Eine quantitative Studie in der Arbeitsdomäne der plattformbasierten Arbeit

Die plattformbasierte Arbeit ist ein stetig wachsender Beschäftigungsbereich. Ins¬besondere Sichtweise, Bewertung, Perspektive und Entwicklung der Mitarbei-terInnen werden gegenwärtig und bezogen auf die zukünftigen Herausforderungen zu selten berücksichtigt. Ziel dieses Artikels ist es, die Ergebnisse einer Online-Umfrage (N=81) zu präsentieren, die 2018 in Deutschland durchgeführt wurde. Von besonderem Interesse waren die folgenden Fragen: (1) Was sind soziodemo¬grafische Merkmale von plattformbasierten Arbeitspersonen? (2) Welche typischen Arbeitsbedingungen gibt es für plattformbasierte Arbeitspersonen? (3) Wie zu¬frieden sind die Beteiligten mit der plattformbasierten Arbeit? Die Teilneh¬merInnen der Umfrage waren überwiegend männlich und jungen Alters, wiesen jedoch unterschiedliche Bildungshintergründe auf. Sie arbeiten überwiegend von zu Hause aus, selten jedoch in den Abendstunden oder am Wochenende. Insgesamt zeigten sich rund zwei Drittel relativ zufrieden.The platform-based gig economy is an increasingly growing area of employment. In particular, the view, assessment, perspective and development of the employees are still and in relation to future challenges rarely taken into account. The aim of this article is to present the results of an online survey (N=81) conducted in Germany in 2018. The following questions were of particular interest: (1) What are sociodemo¬graphic characteristics of platform-based workers? (2) What are typical working conditions of platform-based work? (3) How satisfied are those involved in plat¬form-based work? The participants of the survey were predominantly male and of younger age, yet with diverse educational backgrounds. They often work from home, apart from the evenings or weekends. Overall, about two thirds stated to be relatively satisfied