668 research outputs found
The Role of Multilevel Landau-Zener Interference in Extreme Harmonic Generation
Motivated by the observation of multiphoton electric dipole spin resonance
processes in InAs nanowires, we theoretically study the transport dynamics of a
periodically driven five-level system, modeling the level structure of a
two-electron double quantum dot. We show that the observed multiphoton
resonances, which are dominant near interdot charge transitions, are due to
multilevel Landau-Zener-Stuckelberg-Majorana interference. Here a third energy
level serves as a shuttle that transfers population between the two resonant
spin states. By numerically integrating the master equation we replicate the
main features observed in the experiments: multiphoton resonances (as large as
8 photons), a robust odd-even dependence, and oscillations in the electric
dipole spin resonance signal as a function of energy level detuning
Phonon-Assisted Gain in a Semiconductor Double Quantum Dot Maser
We develop a microscopic model for the recently demonstrated double quantum
dot (DQD) maser. In characterizing the gain of this device we find that, in
addition to the direct stimulated emission of photons, there is a large
contribution from the simultaneous emission of a photon and a phonon, i.e., the
phonon sideband. We show that this phonon-assisted gain typically dominates the
overall gain which leads to masing. Recent experimental data are well fit with
our model.Comment: v1: 6 pgs, 2 figures; v2: 6 pgs, 3 figures, added Fig 2b and Fig. 3b,
modified main text; v3: 6+ pgs, 3 figures, modified main tex
Injection Locking of a Semiconductor Double Quantum Dot Micromaser
Emission linewidth is an important figure of merit for masers and lasers. We
recently demonstrated a semiconductor double quantum dot (DQD) micromaser where
photons are generated through single electron tunneling events. Charge noise
directly couples to the DQD energy levels, resulting in a maser linewidth that
is more than 100 times larger than the Schawlow-Townes prediction. Here we
demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD
emission to a coherent tone that is injected to the input port of the cavity.
We measure the injection locking range as a function of cavity input power and
show that it is in agreement with the Adler equation. The position and
amplitude of distortion sidebands that appear outside of the injection locking
range are quantitatively examined. Our results show that this unconventional
maser, which is impacted by strong charge noise and electron-phonon coupling,
is well described by standard laser models
Influence of tied ridging technology on the rate of surface runoff and erosion in potato cultivation
ArticleWater management and securing good condition of soil is becoming an important
factor in agriculture one of the reasons being adaptation to the increasingly frequent extremes in
weather. Tied ridging technology enables to reduce significantly the loss of water and soil from
arable land. The effect of a tied ridger mounted on 2-row planter and effect of 6-row tied ridger
on basin renewal was tested in potato cultivation on plots of land with length of 10 m. During
entire season lasting 135 days the technology helped achieve 78% of efficiency in reduction of
surface water runoff and 88% of efficiency in case of soil loss. In the case of furrows with only
tied ridging the water retained represented additional 15% of total water from rainfall (37.5 mm
of 250 mm) over untreated furrows. In the case of basins formed in furrows with wheel trails the
water retained represented 15% of total water from rainfalls in the trail. This water retained on
the land would have otherwise flown off and would not have been utilized without this
technology. The renewal of dams after 1/3 of the season increased significantly the efficiency of
this technology. The technology of tied ridging significantly contributes to sustainable agriculture management
Threshold Dynamics of a Semiconductor Single Atom Maser
We demonstrate a single-atom maser consisting of a semiconductor double
quantum dot (DQD) that is embedded in a high quality factor microwave cavity. A
finite bias drives the DQD out of equilibrium, resulting in sequential single
electron tunneling and masing. We develop a dynamic tuning protocol that allows
us to controllably increase the time-averaged repumping rate of the DQD at a
fixed level detuning, and quantitatively study the transition through the
masing threshold. We further examine the crossover from incoherent to coherent
emission by measuring the photon statistics across the masing transition. The
observed threshold behavior is in agreement with an existing single atom maser
theory when small corrections from lead emission are taken into account
Scalable Spin Amplification with a Gain over a Hundred
We propose a scalable and practical implementation of spin amplification
which does not require individual addressing nor a specially tailored spin
network. We have demonstrated a gain of 140 in a solid-state nuclear spin
system of which the spin polarization has been increased to 0.12 using dynamic
nuclear polarization with photoexcited triplet electron spins. Spin
amplification scalable to a higher gain opens the door to the single spin
measurement for a readout of quantum computers as well as practical
applications of nuclear magnetic resonance (NMR) spectroscopy to infinitesimal
samples which have been concealed by thermal noise.Comment: 6 pages, 7 figure
Double Quantum Dot Floquet Gain Medium
Strongly driving a two-level quantum system with light leads to a ladder of
Floquet states separated by the photon energy. Nanoscale quantum devices allow
the interplay of confined electrons, phonons, and photons to be studied under
strong driving conditions. Here we show that a single electron in a
periodically driven DQD functions as a "Floquet gain medium," where population
imbalances in the DQD Floquet quasi-energy levels lead to an intricate pattern
of gain and loss features in the cavity response. We further measure a large
intra-cavity photon number n_c in the absence of a cavity drive field, due to
equilibration in the Floquet picture. Our device operates in the absence of a
dc current -- one and the same electron is repeatedly driven to the excited
state to generate population inversion. These results pave the way to future
studies of non-classical light and thermalization of driven quantum systems
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