2,258 research outputs found
Quantifying the Contribution of Crystallographic Texture and Grain Morphology on the Elastic and Plastic Anisotropy of bcc Steel
Charge transport through a SET with a mechanically oscillating island
We consider a single-electron transistor (SET) whose central island is a
nanomechanical oscillator. The gate capacitance of the SET depends on the
mechanical displacement, thus, the vibrations of the island vibrations may
strongly influence the current-voltage characteristics, current noise, and
higher cumulants of the current. Harmonic oscillations of the island and
oscillations with random amplitude (e.g., due to the thermal activation) change
the transport characteristics in a different way. The noise spectrum has a peak
at the frequency of the island oscillations; when the island oscillates
harmonically, the peak reduces to a -peak. We show that knowledge of
the SET transport properties helps to determine in what way the island
oscillates, to estimate the amplitude, and the frequency of the oscillations
Polaronic signatures and spectral properties of graphene antidot lattices
We explore the consequences of electron-phonon (e-ph) coupling in graphene
antidot lattices (graphene nanomeshes), i.e., triangular superlattices of
circular holes (antidots) in a graphene sheet. They display a direct band gap
whose magnitude can be controlled via the antidot size and density. The
relevant coupling mechanism in these semiconducting counterparts of graphene is
the modulation of the nearest-neighbor electronic hopping integrals due to
lattice distortions (Peierls-type e-ph coupling). We compute the full momentum
dependence of the e-ph vertex functions for a number of representative antidot
lattices. Based on the latter, we discuss the origins of the previously found
large conduction-band quasiparticle spectral weight due to e-ph coupling. In
addition, we study the nonzero-momentum quasiparticle properties with the aid
of the self-consistent Born approximation, yielding results that can be
compared with future angle-resolved photoemission spectroscopy measurements.
Our principal finding is a significant e-ph mass enhancement, an indication of
polaronic behavior. This can be ascribed to the peculiar momentum dependence of
the e-ph interaction in these narrow-band systems, which favors small phonon
momentum scattering. We also discuss implications of our study for recently
fabricated large-period graphene antidot lattices.Comment: published versio
Use of dynamical coupling for improved quantum state transfer
We propose a method to improve quantum state transfer in transmission lines.
The idea is to localize the information on the last qubit of a transmission
line, by dynamically varying the coupling constants between the first and the
last pair of qubits. The fidelity of state transfer is higher then in a chain
with fixed coupling constants. The effect is stable against small fluctuations
in the system parameters.Comment: 5 pages, 7 figure
Quantum state preparation for coupled period tripling oscillators
We investigate the quantum transition to a correlated state of coupled
oscillators in the regime where they display period tripling in response to a
drive at triple the eigenfrequency. Correlations are formed between the
discrete oscillation phases of individual oscillators. The evolution toward the
ordered state is accompanied by the transient breaking of the symmetry between
seemingly equivalent configurations. We attribute this to the nontrivial
geometric phase that characterizes period tripling. We also show that the
Wigner distribution of a single damped quantum oscillator can display a minimum
at the classically stable zero-amplitude state.Comment: 7 pages, 9 figure
Strategy for implementing stabilizer-based codes on solid-state qubits
We present a method for implementing stabilizer-based codes with encoding
schemes of the operator quantum error correction paradigm, e.g., the "standard"
five-qubit and CSS codes, on solid-state qubits with Ising or XY-type
interactions. Using pulse sequences, we show how to induce the effective
dynamics of the stabilizer Hamiltonian, the sum of an appropriate set of
stabilizer operators for a given code. Within this approach, the encoded states
(ground states of the stabilizer Hamiltonian) can be prepared without
measurements and preserved against both the time evolution governed by the
original qubit Hamiltonian, and energy-nonconserving errors caused by the
environment.Comment: 5 pages, 1 figur
Energy based method for numerical fatigue analysis of multidirectional carbon fibre reinforced plastics
This paper describes experiments on multiaxial fibre reinforced plastic laminates, which were performed to obtain calibration data for numerical fatigue analyses. For this purpose, fatigue tests of laminates with multidirectional layers subjected to constant amplitude and block loading (0 <= R<1 or R<1) were analysed. The presented simulation results display the fatigue behaviour of carbon fibre reinforced plastics for unidirectional loading conditions and a selected laminate
Preserving universal resources for one-way quantum computing
The common spin Hamiltonians such as the Ising, XY, or Heisenberg model do
not have ground states that are the graph states needed in measurement-based
quantum computation. Various highly-entangled many-body states have been
suggested as a universal resource for this type of computation, however, it is
not easy to preserve these states in solid-state systems due to their short
coherence times. Here we propose a scheme for generating a Hamiltonian that has
a cluster state as ground state. Our approach employs a series of pulse
sequences inspired by established NMR techniques and holds promise for
applications in many areas of quantum information processing.Comment: 5 pages, 2 figure
Role of interference in quantum state transfer through spin chains
We examine the role that interference plays in quantum state transfer through
several types of finite spin chains, including chains with isotropic Heisenberg
interaction between nearest neighbors, chains with reduced coupling constants
to the spins at the end of the chain, and chains with anisotropic coupling
constants. We evaluate quantitatively both the interference corresponding to
the propagation of the entire chain, and the interference in the effective
propagation of the first and last spins only, treating the rest of the chain as
black box. We show that perfect quantum state transfer is possible without
quantum interference, and provide evidence that the spin chains examined
realize interference-free quantum state transfer to a good approximation.Comment: 10 figure
Neutral edge modes in a superconductor -- topological-insulator hybrid structure in a perpendicular magnetic field
We study the low-energy edge states of a superconductor -- 3D
topological-insulator hybrid structure (NS junction) in the presence of a
perpendicular magnetic field. The hybridization of electron-like and hole-like
Landau levels due to Andreev reflection gives rise to chiral edge states within
each Landau level. We show that by changing the chemical potential of the
superconductor, this junction can be placed in a regime where the sign of the
effective charge of the edge state within the zeroth Landau level changes more
than once resulting in neutral edge modes with a finite value of the
guiding-center coordinate. We find that the appearance of these neutral edge
modes is related to the level repulsion between the zeroth and the first Landau
levels in the spectra. We also find that these neutral edge modes come in
pairs, one in the zeroth Landau level and its corresponding pair in the first.Comment: 5 page
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