1,590 research outputs found
Non-linear spin to charge conversion in mesoscopic structures
Motivated by recent experiments [Vera-Marun et al., arXiv:1109.5969], we
formulate a non-linear theory of spin transport in quantum coherent conductors.
We show how a mesoscopic constriction with energy-dependent transmission can
convert a spin current injected by a spin accumulation into an electric signal,
relying neither on magnetic nor exchange fields. When the transmission through
the constriction is spin-independent, the spin-charge coupling is non-linear,
with an electric signal that is quadratic in the accumulation. We estimate that
gated mesoscopic constrictions have a sensitivity that allows to detect
accumulations much smaller than a percent of the Fermi energy.Comment: 4 pages, 3 figure
Magnetic bipolar transistor
A magnetic bipolar transistor is a bipolar junction transistor with one or
more magnetic regions, and/or with an externally injected nonequilibrium
(source) spin. It is shown that electrical spin injection through the
transistor is possible in the forward active regime. It is predicted that the
current amplification of the transistor can be tuned by spin.Comment: 4 pages, 2 figure
Joint measurement of complementary observables in moment tomography
Wigner and Husimi quasi-distributions, owing to their functional regularity,
give the two archetypal and equivalent representations of all
observable-parameters in continuous-variable quantum information. Balanced
homodyning and heterodyning that correspond to their associated sampling
procedures, on the other hand, fare very differently concerning their state or
parameter reconstruction accuracies. We present a general theory of a now-known
fact that heterodyning can be tomographically more powerful than balanced
homodyning to many interesting classes of single-mode quantum states, and
discuss the treatment for two-mode sources.Comment: 15 pages, 4 figures, conference proceedings for Quantum 2017 in
Torin
Theory of Spin Relaxation in Two-Electron Lateral Coupled Si/SiGe Quantum Dots
Highly accurate numerical results of phonon-induced two-electron spin
relaxation in silicon double quantum dots are presented. The relaxation,
enabled by spin-orbit coupling and the nuclei of Si (natural or purified
abundance), are investigated for experimentally relevant parameters, the
interdot coupling, the magnetic field magnitude and orientation, and the
detuning. We calculate relaxation rates for zero and finite temperatures (100
mK), concluding that our findings for zero temperature remain qualitatively
valid also for 100 mK. We confirm the same anisotropic switch of the axis of
prolonged spin lifetime with varying detuning as recently predicted in GaAs.
Conditions for possibly hyperfine-dominated relaxation are much more stringent
in Si than in GaAs. For experimentally relevant regimes, the spin-orbit
coupling, although weak, is the dominant contribution, yielding anisotropic
relaxation rates of at least two order of magnitude lower than in GaAs.Comment: 11 pages, 10 figure
Minimal qubit tomography
We present, and analyze thoroughly, a highly symmetric and efficient scheme
for the determination of a single-qubit state, such as the polarization
properties of photons emitted by a single-photon source. In our scheme there
are only four measured probabilities, just enough for the determination of the
three parameters that specify the qubit state, whereas the standard procedure
would measure six probabilities.Comment: 14 pages, 10 figures; final versio
Signatures of the non-Maxwellian -distributions in optically thin line spectra. II. Synthetic Fe XVII--XVIII X-ray coronal spectra and predictions for the Marshall Grazing-Incidence X-ray Spectrometer (MaGIXS)
We investigated the possibility of diagnosing the degree of departure from
the Maxwellian distribution using the Fe XVII - Fe XVIII spectra originating in
plasmas in collisional ionization equilibrium, such as in the cores of solar
active regions or microflares. The original collision strengths for excitation
are integrated over the non-Maxwellian electron -distributions
characterized by a high-energy tail. Synthetic X-ray emission line spectra were
calculated for a range of temperatures and . We focus on the 6-24 A
spectral range to be observed by the upcoming Marshall Grazing-Incidence X-ray
Spectrometer MaGIXS. We find that many line intensity ratios are sensitive to
both and . Best diagnostic options are provided if a ratio
involving both Fe XVII and Fe XVIII is combined with another ratio involving
lines formed within a single ion. The sensitivity of such diagnostics to
is typically a few tens of per cent. Much larger sensitivity, of about
a factor of two to three, can be obtained if the Fe XVIII 93.93 A line observed
by SDO/AIA is used in conjuction with the X-ray lines. We conclude that the
MaGIXS instrument is well-suited for detection of departures from the
Maxwellian distribution, especially in active region cores.Comment: Astronomy & Astrophysics, accepte
The Slavic Manuscripts in the Federal Republic of Germany
William R. Veder, Katholieke Universiteit, Nijmegen, Holland. No institutional affiliation is indicated for Heinz Miklas or Jaroslav N. Ščapov.This article, which appears under the section title of "ДѢЛО КЪНИЖЬНОѤ/Dielo k"nizh'noie" in Polata knigopisnaia 9, provides an inventory describing Slavic manuscripts in the Federal Republic of Germany.The inventory indicates the shelfmark, date, language, title, foliation, dimensions, and material (writing support) of the items where known, as well as references to publications about each item. Manuscripts are noted in the following cities: Bamberg, Berlin, Bonn, Erlangen, Göttingen, Hamburg, Hanover, Heidelberg, Karlsruhe, Limburgerhof, München, Bad Soden-Neuenhain, Stuttgart, Tübingen, Wolfenbüttel, Wertheim, Würzberg, and Freiberg. Languages represented include: Bulgarian, Croatian, Czech, French, German, Italian, Latin, Moldavian, Polabian, Polish, Russian, Serbian, and Lower Sorbian. The manuscripts range in date from the 10th to the 19th centuries. The list of references is on pages 52-58
Spin-orbit coupled particle in a spin bath
We consider a spin-orbit coupled particle confined in a quantum dot in a bath
of impurity spins. We investigate the consequences of spin-orbit coupling on
the interactions that the particle mediates in the spin bath. We show that in
the presence of spin-orbit coupling, the impurity-impurity interactions are no
longer spin-conserving. We quantify the degree of this symmetry breaking and
show how it relates to the spin-orbit coupling strength. We identify several
ways how the impurity ensemble can in this way relax its spin by coupling to
phonons. A typical resulting relaxation rate for a self-assembled Mn-doped ZnTe
quantum dot populated by a hole is 1 s. We also show that decoherence
arising from nuclear spins in lateral quantum dots is still removable by a spin
echo protocol, even if the confined electron is spin-orbit coupled.Comment: 18 pages, 1 figur
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