406 research outputs found
Entanglement dynamics of electron-electron scattering in low-dimensional semiconductor systems
We perform the quantitative evaluation of the entanglement dynamics in
scattering events between two insistinguishable electrons interacting via
Coulomb potential in 1D and 2D semiconductor nanostructures. We apply a
criterion based on the von Neumann entropy and the Schmidt decomposition of the
global state vector suitable for systems of identical particles. From the
timedependent numerical solution of the two-particle wavefunction of the
scattering carriers we compute their entanglement evolution for different spin
configurations: two electrons with the same spin, with different spin, singlet,
and triplet spin state. The procedure allows to evaluate the mechanisms that
govern entanglement creation and their connection with the characteristic
physical parameters and initial conditions of the system. The cases in which
the evolution of entanglement is similar to the one obtained for
distinguishable particles are discussed.Comment: 22 pages, 7 figures, submitted to Physical Review
Dynamics of copropagating edge states in a multichannel Mach-Zender interferometer
We study numerically a multichannel electronic Mach-Zender interferometer, where
an orthogonal magnetic field produces edge states. Our time-dependent model is based on the split-step Fourier method and describes the charge carrier as a Gaussian wavepacket of edge states, whose path is defined by split-gate induced potential profiles on the 2DEG at filling factor 2. We analyse a beam splitter with ∼ 50% inter-channel mixing and obtain Aharonov-Bohm oscillations in the transmission probability of the second channel
Transport efficiency of continuous-time quantum walks on graphs
Continuous-time quantum walk describes the propagation of a quantum particle (or an excitation) evolving continuously in time on a graph. As such, it provides a natural framework for modeling transport processes, e.g., in light-harvesting systems. In particular, the transport properties strongly depend on the initial state and specific features of the graph under investigation. In this paper, we address the role of graph topology, and investigate the transport properties of graphs with different regularity, symmetry, and connectivity. We neglect disorder and decoherence, and assume a single trap vertex that is accountable for the loss processes. In particular, for each graph, we analytically determine the subspace of states having maximum transport efficiency. Our results provide a set of benchmarks for environment-assisted quantum transport, and suggest that connectivity is a poor indicator for transport efficiency. Indeed, we observe some specific correlations between transport efficiency and connectivity for certain graphs, but, in general, they are uncorrelated
Carrier-carrier entanglement and transport resonances in semiconductor quantum dots
We study theoretically the entanglement created in a scattering between an
electron, incoming from a source lead, and another electron bound in the ground
state of a quantum dot, connected to two leads. We analyze the role played by
the different kinds of resonances in the transmission spectra and by the number
of scattering channels, into the amount of quantum correlations between the two
identical carriers. It is shown that the entanglement between their energy
states is not sensitive to the presence of Breit-Wigner resonances, while it
presents a peculiar behavior in correspondence of Fano peaks: two close maxima
separated by a minimum, for a two-channel scattering, a single maximum for a
multi-channel scattering. Such a behavior is ascribed to the different
mechanisms characterizing the two types of resonances. Our results suggest that
the production and detection of entanglement in quantum dot structures may be
controlled by the manipulation of Fano resonances through external fields.Comment: 8 pages, 6 figures, RevTex4 two-column format, submitte
On demand entanglement in double quantum dots via coherent carrier scattering
We show how two qubits encoded in the orbital states of two quantum dots can
be entangled or disentangled in a controlled way through their interaction with
a weak electron current. The transmission/reflection spectrum of each scattered
electron, acting as an entanglement mediator between the dots, shows a
signature of the dot-dot entangled state. Strikingly, while few scattered
carriers produce decoherence of the whole two-dots system, a larger number of
electrons injected from one lead with proper energy is able to recover its
quantum coherence. Our numerical simulations are based on a real-space solution
of the three-particle Schroedinger equation with open boundaries. The computed
transmission amplitudes are inserted in the analytical expression of the system
density matrix in order to evaluate the entanglement.Comment: 20 pages, 5 figure
Quantum Transport in a Nanosize Silicon-on-Insulator Metal-Oxide-Semiconductor
An approach is developed for the determination of the current flowing through
a nanosize silicon-on-insulator (SOI) metal-oxide-semiconductor field-effect
transistors (MOSFET). The quantum mechanical features of the electron transport
are extracted from the numerical solution of the quantum Liouville equation in
the Wigner function representation. Accounting for electron scattering due to
ionized impurities, acoustic phonons and surface roughness at the Si/SiO2
interface, device characteristics are obtained as a function of a channel
length. From the Wigner function distributions, the coexistence of the
diffusive and the ballistic transport naturally emerges. It is shown that the
scattering mechanisms tend to reduce the ballistic component of the transport.
The ballistic component increases with decreasing the channel length.Comment: 21 pages, 8 figures, E-mail addresses: [email protected]
Laser Viewing System for In-Vessel Inspection and Control in Large Fusion Machines (JET and ITER)
Harvard Law School Lambda Second Annual Gay and Lesbian Legal Advocacy Conference: “Don’t Ask, Don’t Tell”
Rank-one flavor violation and B-meson anomalies
We assume that the quark-flavor coefficients matrix of the semileptonic operators addressing the neutral-current B-meson anomalies has rank-one, i.e. it can be described by a single vector in quark-flavor space. By correlating the observed anomalies to other flavor and high-pT observables, we constrain its possible directions and we show that a large region of the parameter space of this framework will be explored by flavor data from the NA62, KOTO, LHCb and Belle II experiments
The risk stratification of adverse neonatal outcomes in women with gestational diabetes (STRONG) study
Aims: To assess the risk of adverse neonatal outcomes in women with gestational diabetes (GDM) by identifying subgroups of women at higher risk to recognize the characteristics most associated with an excess of risk. Methods: Observational, retrospective, multicenter study involving consecutive women with GDM. To identify distinct and homogeneous subgroups of women at a higher risk, the RECursive Partitioning and AMalgamation (RECPAM) method was used. Overall, 2736 pregnancies complicated by GDM were analyzed. The main outcome measure was the occurrence of adverse neonatal outcomes in pregnancies complicated by GDM. Results: Among study participants (median age 36.8 years, pre-gestational BMI 24.8 kg/m2), six miscarriages, one neonatal death, but no maternal death was recorded. The occurrence of the cumulative adverse outcome (OR 2.48, 95% CI 1.59–3.87), large for gestational age (OR 3.99, 95% CI 2.40–6.63), fetal malformation (OR 2.66, 95% CI 1.00–7.18), and respiratory distress (OR 4.33, 95% CI 1.33–14.12) was associated with previous macrosomia. Large for gestational age was also associated with obesity (OR 1.46, 95% CI 1.00–2.15). Small for gestational age was associated with first trimester glucose levels (OR 1.96, 95% CI 1.04–3.69). Neonatal hypoglycemia was associated with overweight (OR 1.52, 95% CI 1.02–2.27) and obesity (OR 1.62, 95% CI 1.04–2.51). The RECPAM analysis identified high-risk subgroups mainly characterized by high pre-pregnancy BMI (OR 1.68, 95% CI 1.21–2.33 for obese; OR 1.38 95% CI 1.03–1.87 for overweight). Conclusions: A deep investigation on the factors associated with adverse neonatal outcomes requires a risk stratification. In particular, great attention must be paid to the prevention and treatment of obesity
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