1,546 research outputs found
Superradiance-like Electron Transport through a Quantum Dot
We theoretically show that intriguing features of coherent many-body physics
can be observed in electron transport through a quantum dot (QD). We first
derive a master equation based framework for electron transport in the
Coulomb-blockade regime which includes hyperfine (HF) interaction with the
nuclear spin ensemble in the QD. This general tool is then used to study the
leakage current through a single QD in a transport setting. We find that, for
an initially polarized nuclear system, the proposed setup leads to a strong
current peak, in close analogy with superradiant emission of photons from
atomic ensembles. This effect could be observed with realistic experimental
parameters and would provide clear evidence of coherent HF dynamics of nuclear
spin ensembles in QDs.Comment: 21 pages, 10 figure
Hybrid Architecture for Engineering Magnonic Quantum Networks
We show theoretically that a network of superconducting loops and magnetic
particles can be used to implement magnonic crystals with tunable magnonic band
structures. In our approach, the loops mediate interactions between the
particles and allow magnetic excitations to tunnel over long distances. As a
result, different arrangements of loops and particles allow one to engineer the
band structure for the magnonic excitations. Furthermore, we show how magnons
in such crystals can serve as a quantum bus for long-distance magnetic coupling
of spin qubits. The qubits are coupled to the magnets in the network by their
local magnetic-dipole interaction and provide an integrated way to measure the
state of the magnonic quantum network.Comment: Manuscript: 4 pages, 3 figures. Supplemental Material: 9 pages, 4
figures. V2: Published version in PRA: 14 pages + 8 figures. Substantial
rearrangement of the content of the previous versio
Nuclear Spin Dynamics in Double Quantum Dots: Multi-Stability, Dynamical Polarization, Criticality and Entanglement
We theoretically study the nuclear spin dynamics driven by electron transport
and hyperfine interaction in an electrically-defined double quantum dot (DQD)
in the Pauli-blockade regime. We derive a master-equation-based framework and
show that the coupled electron-nuclear system displays an instability towards
the buildup of large nuclear spin polarization gradients in the two quantum
dots. In the presence of such inhomogeneous magnetic fields, a quantum
interference effect in the collective hyperfine coupling results in sizable
nuclear spin entanglement between the two quantum dots in the steady state of
the evolution. We investigate this effect using analytical and numerical
techniques, and demonstrate its robustness under various types of
imperfections.Comment: 35 pages, 19 figures. This article provides the full analysis of a
scheme proposed in Phys. Rev. Lett. 111, 246802 (2013). v2: version as
publishe
Expansion velocity of a one-dimensional, two-component Fermi gas during the sudden expansion in the ballistic regime
We show that in the sudden expansion of a spin-balanced two-component Fermi
gas into an empty optical lattice induced by releasing particles from a trap,
over a wide parameter regime, the radius of the particle cloud grows
linearly in time. This allow us to define the expansion velocity from
. The goal of this work is to clarify the dependence of the
expansion velocity on the initial conditions which we establish from
time-dependent density matrix renormalization group simulations, both for a box
trap and a harmonic trap. As a prominent result, the presence of a
Mott-insulating region leaves clear fingerprints in the expansion velocity. Our
predictions can be verified in experiments with ultra-cold atoms.Comment: 8 pages 10 figures, version as published with minor stylistic change
Mixed population of competing TASEPs with a shared reservoir of particles
We introduce a mean-field theoretical framework to describe multiple totally
asymmetric simple exclusion processes (TASEPs) with different lattice lengths,
entry and exit rates, competing for a finite reservoir of particles. We present
relations for the partitioning of particles between the reservoir and the
lattices: these relations allow us to show that competition for particles can
have non-trivial effects on the phase behavior of individual lattices. For a
system with non-identical lattices, we find that when a subset of lattices
undergoes a phase transition from low to high density, the entire set of
lattice currents becomes independent of total particle number. We generalize
our approach to systems with a continuous distribution of lattice parameters,
for which we demonstrate that measurements of the current carried by a single
lattice type can be used to extract the entire distribution of lattice
parameters. Our approach applies to populations of TASEPs with any distribution
of lattice parameters, and could easily be extended beyond the mean-field case.Comment: 12 pages, 8 figure
Crop Knowledge Discovery Based on Agricultural Big Data Integration
Nowadays, the agricultural data can be generated through various sources,
such as: Internet of Thing (IoT), sensors, satellites, weather stations,
robots, farm equipment, agricultural laboratories, farmers, government agencies
and agribusinesses. The analysis of this big data enables farmers, companies
and agronomists to extract high business and scientific knowledge, improving
their operational processes and product quality. However, before analysing this
data, different data sources need to be normalised, homogenised and integrated
into a unified data representation. In this paper, we propose an agricultural
data integration method using a constellation schema which is designed to be
flexible enough to incorporate other datasets and big data models. We also
apply some methods to extract knowledge with the view to improve crop yield;
these include finding suitable quantities of soil properties, herbicides and
insecticides for both increasing crop yield and protecting the environment.Comment: 5 page
Measuring the Impact of Agglomeration on Productivity: Evidence from Chilean Retailers
This research extends the agglomeration literature to a country that has not been studied and a market sector that has received little attention. The majority of research that examines how density affects productivity has indirectly measured productivity through worker wages or property prices. The research uses individual supermarkets’ store productivity, proxied by 10 years of annual sales per square foot. Studying supermarkets permits the examination of the effect consumers might have on productivity. Agglomerations (density) could increase or decrease productivity depending on the relative extent of increased competition versus productivity gains, as consumers choose where to shop based on their interests in reducing shopping time (transport costs) and comparison shopping (product quality and pricing). Stores are described by who operates the store, the brand of the store and the size of the store. Results indicate that density has a differential impact depending on the store itself and the mix of stores nearby
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