Time-dependent transport in Graphene Mach-Zender Interferometers

Graphene nanoribbons provide an ideal platform for electronic interferometry in the Integer Quantum Hall regime. Here, we solve the time-dependent four-component Schroedinger equation for single carriers in graphene and expose several dynamical effects of the carrier localization on their transport characteristics in pn junctions. We simulate two kinds of Mach-Zender Interferometers (MZI). The first is based on Quantum Point Contacts and is similar to traditional GaAs/AlGaAs interferometers. As expected, we observe Aharonov-Bohm oscillations and phase averaging. The second is based on Valley Beam Splitters, where we observe unexpected phenomena due to the intersection of the Edge Channels that constitute the MZI. Our results provide further insights into the behavior of graphene interferometers. Additionally, they highlight the operative regime of such nanodevices for feasible single-particle implementations.Comment: 14 pages, 7 figure

Two-electron selective coupling in an edge-state based conditional phase shifter

We investigate the effect of long-range Coulomb interaction on the two-electron scattering in the integer quantum Hall regime at bulk filling factor two.We compute the dynamics of the exact two-particle wave function by means of a parallel version of the split-step Fourier method in a 2D potential background reproducing the effect of depleting gates in a realistic heterostructure, with the charge carrier represented by a localized wave packet of edge states.We compare the spatial shift induced by Coulomb repulsion in the final two-electron wave function for two indistinguishable electrons initialized in different configurations according to their Landau index and analyze their bunching probability and the effect of screening. We finally prove the feasibility of this device as a two-qubit conditional phase shifter able to generate controlled entanglement from product states

Adhesion, Friction and Tribochemical Reactions at the Diamond-Silica Interface

Diamond-based coatings are employed in several technological applications, for their outstanding mechanical properties, biocompatibility, and chemical stability. Of significant relevance is the interface with silicon oxide, where phenomena of adhesion, friction, and wear can affect drastically the performance of the coating. Here we monitor such phenomena in real-time by performing massive ab initio molecular dynamics simulations in tribological conditions. We take into account many relevant factors that can play a role, i.e. the diamond surface orientation and reconstruction, silanol density, as well as, the type and concentration of passivating species. The large systems size and the long simulations time, put our work at the frontier of what can be currently done with fully ab initio molecular dynamics. The results of our work point to full hydrogenation as an effective way to reduce both friction and wear for all diamond surfaces, while graphitization is competitive only on the (111) surface. Overall we expect that our observations will be useful to improve technological applications where the silica-diamond interface plays a key role. Moreover, we demonstrate that realistic and accurate in silico experiments are feasible nowadays exploiting HPC resources and HPC optimized software, paving the way to a more general understanding of the relationship between surface chemistry and nanoscale-tribology

Quantum estimation and remote charge sensing with a hole-spin qubit in silicon

Hole-spin qubits in semiconductors represent a mature platform for quantum technological applications. Here we consider their use as quantum sensors, and specifically for inferring the presence and estimating the distance from the qubit of a remote charge. Different approaches are considered, based on the use of single or double quantum dots, ground and out-of-equilibrium states, Rabi and Ramsey measurements, and comparatively analyzed by means of the discrimination probability, and of the classical and quantum Fisher information. Detailed quantitative aspects result from the multiband character of the hole states, which we account for by means of the Luttinger-Kohn Hamiltonian. Furthermore, general conclusions can be drawn on the relative efficiency of the above options, and analytical expressions are derived for the Fisher information of a generic qubit within the Rabi and Ramsey schemes

Acquired Hearing Loss, Anger, and Emotional Distress: The Mediating Role of Perceived Disability

The aim of the study was to test whether acquired hearing loss (AHL)-related perceived disability mediates the association between AHL and psychological outcomes, including anger. Two-hundred ninety-seven consecutive outpatients with AHL assessed by pure tone average (PTA) loss completed the following: Hearing Handicap Inventory for Adults (HHIA), State-Trait Anger Expression Inventory-2 (STAXI-2), Brief Symptom Inventory (BSI), Diagnostic Criteria for Use in Psychosomatic Research (DCPR), and Social Functioning Questionnaire. In the sample, composed of 44.5% males with a mean age of 53.8 and a mean PTA of 30.7, AHL was associated to perceived hearing handicap, also correlating to all psychological measures except DCPR demoralization. Associations were stronger between the HHIA-Emotional Subscale, STAXI-2 State Anger and Feeling Angry, and BSI-Somatization, Interpersonal Sensitivity, Depression, and Psychoticism. Perceived disability predicted the presence of almost all psychosocial outcomes and confirms to be the most significant target of clinical action