Conductance fluctuations and boundary conditions

The conductance fluctuations for various types for two-- and three--dimensional disordered systems with hard wall and periodic boundary conditions are studied, all the way from the ballistic (metallic) regime to the localized regime. It is shown that the universal conductance fluctuations (UCF) depend on the boundary conditions. The same holds for the metal to insulator transition. The conditions for observing the UCF are also given.Comment: 4 pages RevTeX, 5 figures include

Electric coupling to the magnetic resonance of split ring resonators

We study both theoretically and experimentally the transmission properties of a lattice of split ring resonators (SRRs) for different electromagnetic (EM) field polarizations and propagation directions. We find unexpectedly that the incident electric field E couples to the magnetic resonance of the SRR when the EM waves propagate perpendicular to the SRR plane and the incident E is parallel to the gap-bearing sides of the SRR. This is manifested by a dip in the transmission spectrum. A simple analytic model is introduced to explain this interesting behavior.Comment: 4 pages, 4 figure

Effect of hydrogen adsorption on the quasiparticle spectra of graphene

We use the non-interacting tight-binding model to study the effect of isolated hydrogen adsorbates on the quasiparticle spectra of single-layer graphene. Using the Green's function approach, we obtain analytic expressions for the local density of states and the spectral function of hydrogen-doped graphene, which are also numerically evaluated and plotted. Our results are relevant for the interpretation of scanning tunneling microscopy and angle-resolved photoemission spectroscopy data of functionalized graphene.Comment: 4 pages, 3 figures, minor corrections to tex

Fast Two-Qubit Gates in Semiconductor Quantum Dots using a Photonic Microcavity

Implementations for quantum computing require fast single- and multi-qubit quantum gate operations. In the case of optically controlled quantum dot qubits theoretical designs for long-range two- or multi-qubit operations satisfying all the requirements in quantum computing are not yet available. We have developed a design for a fast, long-range two-qubit gate mediated by a photonic microcavity mode using excited states of the quantum dot-cavity system that addresses these needs. This design does not require identical qubits, it is compatible with available optically induced single qubit operations, and it advances opportunities for scalable architectures. We show that the gate fidelity can exceed 90% in experimentally accessible systems

A hidden semi-Markov model for characterising regime shifts in ocean density variability

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordSocietally important decadal predictions of temperature and precipitation over Europe are largely affected by variability in the North Atlantic Ocean. Within this region, the Labrador Sea is of particular importance due its link between surface-driven density variability and the Atlantic Meridional Overturning Circulation (AMOC). Using physical justifications, we propose a statistical model to describe the temporal variability of ocean density in terms of salinity-driven and temperature-driven density. This is a hidden semi-Markov model that allows for either a salinity-driven or a temperature-driven ocean density regime, such that the persistence in each regime is governed probabilistically by a semiMarkov chain. The model is fitted in the Bayesian framework, and a reversible MCMC algorithm is proposed to deal with a single-regime scenario. The model is first applied to a reanalysis data set, where model checking measures are also proposed. Then it is applied to data from 43 climate models to investigate whether and how ocean density variability differs between them and also the reanalysis data. Parameter estimates relating to the mean holding time for each regime are used to establish a link between regime behaviour and the AMOC

Work-In-Progress Paper: WebXR to support student wellbeing and anxiety

The COVID-19 pandemic social distancing measures had immense evidenced impact on student life in higher education affecting their mental health in many ways. In addition, remote working measures taken by Higher Education organizations to protect students and staff created an additional barrier for students seeking support at a stage they feel the most vulnerable. This paper presents a work-in-progress study that focuses on investigating ways of designing an online system for self-assessment symptoms of anxiety based on which available support is provided in a personalized and emotionally engaging manner. The project builds and compares three prototypes: a conventional web site; a VR immersive environment with a single virtual human playing the role of a student life advisor; and an immersive environment with more than one virtual humans interacting with the user aiming to study which system engages and assists vulnerable students more effectively, contributing to a better user experience. The paper presents that project motivations, its aims and objectives, the proposed research methodology and the expected contributions to knowledge