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Bi2Se3 topological insulator quantum wires
We study the effect of 3D topological insulator (TI) contributions to the band structure and wavefunctions of quasi-one-dimensional electron systems (Q1DES). Our model for this system consists of an effective Hamiltonian derived previously in the literature from the crystal symmetries of Bi2Se3. We find that in wires whose face lies in the plane formed by the y and z crystal directions and whose width is around 25 quintuple layers or more, the bands nearest to the gap are non-monotonic; we show that this has implications for the conductance of the wire. In addition, we observed increasing penetration depth of surface states with increasing wavenumber of the propagating mode. We believe these results have qualitative relevance to the family of 3D topological insulators whose crystal structure is characterised by the space group Equation 1, and that the work done here contributes to the wider field of the study of conductance in topological insulators
Where and Who? Automatic Semantic-Aware Person Composition
Image compositing is a method used to generate realistic yet fake imagery by
inserting contents from one image to another. Previous work in compositing has
focused on improving appearance compatibility of a user selected foreground
segment and a background image (i.e. color and illumination consistency). In
this work, we instead develop a fully automated compositing model that
additionally learns to select and transform compatible foreground segments from
a large collection given only an input image background. To simplify the task,
we restrict our problem by focusing on human instance composition, because
human segments exhibit strong correlations with their background and because of
the availability of large annotated data. We develop a novel branching
Convolutional Neural Network (CNN) that jointly predicts candidate person
locations given a background image. We then use pre-trained deep feature
representations to retrieve person instances from a large segment database.
Experimental results show that our model can generate composite images that
look visually convincing. We also develop a user interface to demonstrate the
potential application of our method.Comment: 10 pages, 9 figure
Surface Acoustic Wave Single-Electron Interferometry
We propose an experiment to observe interference of a single electron as it
is transported along two parallel quasi-one-dimensional channels trapped in a
single minimum of a travelling periodic electric field. The experimental device
is a modification of the surface acoustic wave (SAW) based quantum processor.
Interference is achieved by creating a superposition of spatial wavefunctions
between the two channels and inducing a relative phase shift via either a
transverse electric field or a magnetic field. The interference can be used to
estimate the decoherence time of an electron in this type of solid-state
device
Charge qubits based on ultra-thin topological insulator films
We study how to use the surface states in a BiSe topological
insulator ultra-thin film that are affected by finite size effects for the
purpose of quantum computing. We demonstrate that: (i) surface states under the
finite size effect can effectively form a two-level system where their energy
levels lie in between the bulk energy gap and a logic qubit can be constructed,
(ii) the qubit can be initialized and manipulated using electric pulses of
simple forms, (iii) two-qubit entanglement is achieved through a
operation when the two qubits are in a parallel setup, and
(iv) alternatively, a Floquet state can be exploited to construct a qubit and
two Floquet qubits can be entangled through a Controlled-NOT operation. The
Floquet qubit offers robustness to background noise since there is always an
oscillating electric field applied, and the single qubit operations are
controlled by amplitude modulation of the oscillating field, which is
convenient experimentally.Comment: 12 pages, 9 figures, submitted to the journal Frontiers of Physic
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