157 research outputs found
Manipulating Atom-Cavity Interactions with Configurable Atomic Chains
We investigate a ring cavity comprising two degenerate counter-propagating
modes coupled to a one-dimensional atomic chain, leading to bidirectional light
scattering. The spatial configuration of the atomic chain, described by a
structure factor, plays a crucial role in manipulation of the atom-cavity
interactions and formation of the collective excitation modes. Remarkably, we
observe that a cavity dark mode is induced when the atomic spacing is an
integer multiple of half-wavelength. The nodes of this standing-wave dark mode
align precisely with the atomic positions, enabling intracavity field
conversion without free space scattering. By adjusting the configuration of the
atomic chain, we realize optical mode conversion with almost no photon loss and
a broad tuning range, making it suitable for various practical applications in
quantum technologies
Engineering the interactions and dynamics of ultracold atom gases
Ultracold atoms are used to study various fundamental physics, including many-body system, nonequilibrium dynamics, and find many applications in quantum computing and quantum sensing. In this thesis, we studied the dynamics of ultracold atom gases with controllable two-body interactions. One of the major concerns is to manipulate the atomic states with electromagnetic fields. Here, we will show four projects associated with this topic.
The first project is about the Sagnac interferometer based on trapped Bose-Einstein condensate. We explored the dynamics of the atoms and their relation to the sensitivity. We came up with an optimised driving field, and the performance is examined with interactions taken into consideration.
The second project is about the quantum dynamics of bosonic atoms in an optical lattice with long-range interactions by Rydberg-dressing. It has been widely studied due to its controllable strength, length and anisotropy, which paves the new approach to engineering exotic quantum states and improving the performance of quantum devices. We found that phase transitions of Mott-insulator, superfluid supersolid, and density wave during a quench process. The correlation of the atoms is studied which reveals the properties of long-range interactions.
The third project shows new designs of the magneto-optical trap for atom cooling. They are proposed to be manufactured by 3D printing technology. We simulated their performance and optimised the geometric parameters. The time-response and impedance have also been analysed.
The fourth project studies the ground state of Rydberg-dressed fermions from the perspective of Fermi surface deformation. We calculated the deformation manifested by the aspect ratio and the appearance of Cooper pairs. The power-law scaling relations have been found with respect to the laser field, atom density and the quantum number of Rydberg states
The Business Talents Cultivation of Cross-border E-commerce under “the Belt and Road Initiative”
Along with “the Belt and Road Initiative”, China’s cross-border e-commerce has been developed rapidly, which will certainly bring new challenges for talents cultivation in the Higher Education. The paper analyzes the new requirements for business talents under cross-border e-commerce. And then a cultivation system was proposed by examining the five major programs in our university. The cultivation objectives, the curriculum and the practical module are elaborated. Finally, some suggestions on the implementation of this cultivation system are put forward
Controlling the dynamical scale factor in a trapped atom Sagnac interferometer
Sagnac interferometers with massive particles promise unique advantages in achieving high-precision measurements of rotation rates over their optical counterparts. Recent proposals and experiments are exploring nonballistic Sagnac interferometers where trapped atoms are transported along a closed path. This is achieved by using superpositions of internal quantum states and their control with state-dependent potentials. We address emergent questions regarding the dynamical behavior of Bose-Einstein condensates in such an interferometer and its impact on rotation sensitivity. We investigate complex dependencies on atomic interactions as well as trap geometries, rotation rates, and speed of operation. We find that temporal transport profiles obtained from a simple optimization strategy for noninteracting particles remain surprisingly robust also in the presence of interactions over a large range of realistic parameters. High sensitivities can be achieved for short interrogation times far from the adiabatic regime. This highlights a route to building fast and robust guided-ring Sagnac interferometers with fully trapped atoms
Quench dynamics of Rydberg-dressed bosons on two-dimensional square lattices
We study dynamics of bosonic atoms on a two dimensional square lattice, where atomic interactions are long ranged with either a box or soft-core shape. The latter can be realized through laser dressing ground state atoms to electronically excited Rydberg states. When the range of interactions is equal or larger than the lattice constant, the system is governed by an extended Bose-Hubbard model. We propose a quench process by varying the atomic hopping linearly across phase boundaries of the Mott insulator-supersolid and supersolid-superfluid phases. Starting from a Mott insulator state, dynamical evolution exhibits a universal behaviour at the early stage. We numerically find that the universality is largely independent of interactions during this stage. However, dynamical evolution could be significantly altered by long-range interactions at later times. We demonstrate that density wave excitations are important below a critical quench rate, where non-universal dynamics is found. We also show that the quench dynamics can be analysed through time-of-flight images, i.e. measuring the momentum distribution and noise correlations
Dynamic Structure in Four-strategy Game: Theory and Experiment
Game dynamics theory, as a field of science, the consistency of theory and
experiment is essential. In the past 10 years, important progress has been made
in the merging of the theory and experiment in this field, in which dynamics
cycle is the presentation. However, the merging works have not got rid of the
constraints of Euclidean two-dimensional cycle so far. This paper uses a
classic four-strategy game to study the dynamic structure (non-Euclidean
superplane cycle). The consistency is in significant between the three ways:
(1) the analytical results from evolutionary dynamics equations, (2)
agent-based simulation results from learning models and (3) laboratory results
from human subjects game experiments. The consistency suggests that, game
dynamic structure could be quantitatively predictable, observable and
controllable in general.Comment: game theory; laboratory game experiment; eigenvector; dynamics system
theor
Calico Salmon Migration Algorithm: A novel meta-heuristic optimization algorithm
A novel population-based optimization method is proposed in this paper, the
Calico Salmon Migration Algorithm (CSMA), which is inspired by the natural
behavior of calico salmon during their migration for mating. The CSMA
optimization process comprises four stages: selecting the search space by
swimming into the river, expanding the search space from the river into the
ocean, performing precise search during the migrating process, and breeding new
subspecies by the remaining calico salmon population. To evaluate the
effectiveness of the new optimizer, we conducted a series of experiments using
different optimization problems and compared the results with various
optimization algorithms in the literature. The numerical experimental results
for benchmark functions demonstrate that the proposed CSMA outperforms other
competing optimization algorithms in terms of convergence speed, accuracy, and
stability. Furthermore, the Friedman ranking test shows that the CSMA is ranked
first among similar algorithms
Enhanced magnetoassociation of Li in the quantum degenerate regime
We study magnetic Feshbach resonance of ultracold Li atoms in a dipole
trap close to quantum degeneracy. The experiment is carried out by linearly
ramping down the magnetic field from the BCS to the BEC side around the broad
resonance at G. The Feshbach molecule formation efficiency depends
strongly on the temperature of the atomic gas and the rate at which the
magnetic field is ramped across the Feshbach resonance. The molecular
association process is well described by the Landau-Zener transition while
above the Fermi temperature, such that two-body physics dominates the dynamics.
However, we observe an enhancement of the atom-molecule coupling as the
Fermionic atoms reach degeneracy, demonstrating the importance of many-body
coherence not captured by the conventional Landau-Zener model. We develop a
theoretical model that explains the temperature dependence of the atom-molecule
coupling. Furthermore, we characterize this dependence experimentally and
extract the atom-molecule coupling coefficient as a function of temperature,
finding qualitative agreement between our model and experimental results.
Accurate measurement of this coupling coefficient is important for both
theoretical and experimental studies of atom-molecule association dynamics.Comment: 6 pages, 4 figure
A Collaborative Jamming Algorithm Based on Multi-UAV Scheduling
In this paper, we consider the problem of multi-unmanned aerial vehicles'
scheduling for cooperative jamming, where UAVs equipped with directional
antennas perform collaborative jamming tasks against several targets of
interest. To ensure effective jamming towards the targets, we formulate it as
an non-convex optimization problem, aiming to minimize the communication
performance of the targets by jointly optimizing UAVs' deployment and
directional antenna orientations. Due to the unique structure of the problem,
we derive an equivalent transformation by introducing a set of auxiliary
matrices. Subsequently, we propose an efficient iterative algorithm based on
the alternating direction method of multipliers, which decomposes the problem
into multiple tractable subproblems solved in closed-form or by gradient
projection method. Extensive simulations validate the efficacy of the proposed
algorithm
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