350 research outputs found
Hidden vortices in a Bose-Einstein condensate in a rotating double-well potential
We study vortex formation in a Bose-Einstein condensate in a rotating
double-well potential. Besides the ordinary quantized vortices and elusive
ghost vortices, "hidden" vortices are found distributing along the central
barrier. These hidden vortices are invisible like ghost vortex but carry
angular momentum. Moreover, their core size is not given by the healing length,
but is strongly influenced by the external potential. We find that the
Feynman's rule can be well satisfied only after including the hidden vortices.
There is no critical rotating frequency for the formation of hidden vortex
while there is one for the formation of ordinary visible vortices. Hidden
vortices can be revealed in the free expansion of the Bose-Einstein
condensates. In addition, the hidden vortices in a Bose-Einstein condensate can
appear in other external potentials, such as a rotating anisotropic toroidal
trap.Comment: 6pages,5figure
Magnetized Accretion Disks with Outflows for Changing-look AGNs
Changing-look active galactic nuclei (CL-AGNs) challenges the standard
accretion theory owing to its rapid variability. Recent numerical simulations
have shown that, for the sub-Eddington accretion case, the disk is magnetic
pressure-dominated, thermally stable, and geometrically thicker than the
standard disk. In addition, outflows were found in the simulations.
Observationally, high blueshifted velocities absorption lines indicate that
outflows exist in AGNs. In this work, based on the simulation results, we
investigate the magnetic pressure-dominated disk, and find that the accretion
timescale is significantly shorter than that of the standard thin disk.
However, such a timescale is still longer than that of the CL-AGNs. Moreover,
if the role of outflows is taken into account, then the accretion timescale can
be even shortened. By the detailed comparison of the theoretical accretion
timescale with the observations, we propose that the magnetic
pressure-dominated disk incorporating outflows can be responsible for the rapid
variability of CL-AGNs.Comment: 11 pages, 3 figures, accepted for publication in Ap
4,4′-{[4-(2,2′:6′,2′′-Terpyridin-4′-yl)phenyl]imino}dibenzaldehyde
The central pyridine ring of the 2,2′:6′,2′′-terpyridine fragment of the title compound, C35H24N4O2, forms dihedral angles of 8.3 (2), 10.6 (3) and 39.4 (3)°, respectively, with the two outer pyridine rings and the attached benzene ring. In the crystal, weak C—H⋯O interactions link the molecules into chains in [010]
Taiji Data Challenge for Exploring Gravitational Wave Universe
The direct observation of gravitational waves (GWs) opens a new window for
exploring new physics from quanta to cosmos and provides a new tool for probing
the evolution of universe. GWs detection in space covers a broad spectrum
ranging over more than four orders of magnitude and enables us to study rich
physical and astronomical phenomena. Taiji is a proposed space-based GW
detection mission that will be launched in the 2030s. Taiji will be exposed to
numerous overlapping and persistent GW signals buried in the foreground and
background, posing various data analysis challenges. In order to empower
potential scientific discoveries, the Mock LISA Data Challenge and the LISA
Data Challenge (LDC) were developed. While LDC provides a baseline framework,
the first LDC needs to be updated with more realistic simulations and adjusted
detector responses for Taiji's constellation. In this paper, we review the
scientific objectives and the roadmap for Taiji, as well as the technical
difficulties in data analysis and the data generation strategy, and present the
associated data challenges. In contrast to LDC, we utilize second-order
Keplerian orbit and second-generation time delay interferometry techniques.
Additionally, we employ a new model for the extreme-mass-ratio inspiral
waveform and stochastic GW background spectrum, which enables us to test
general relativity and measure the non-Gaussianity of curvature perturbations.
Furthermore, we present a comprehensive showcase of parameter estimation using
a toy dataset. This showcase not only demonstrates the scientific potential of
the Taiji Data Challenge but also serves to validate the effectiveness of the
pipeline. As the first data challenge for Taiji, we aim to build an open ground
for data analysis related to Taiji sources and sciences. More details can be
found on the official website at http://taiji-tdc.ictp-ap.org.Comment: 15 pages, 3 figure
Symmetry and -Enhanced Quantum Sensing in a Spin-Boson System
Open systems, governed by non-Hermitian Hamiltonians, evolve fundamentally
differently from their Hermitian counterparts and facilitate many unusual
applications. Although non-Hermitian but parity-time () symmetric
dynamics has been realized in a variety of classical or semiclassical systems,
its fully quantum-mechanical demonstration is still lacking. Here we
ingeniously engineer a highly controllable anti-Hermitian spin-boson model in a
circuit quantum-electrodynamical structure composed of a decaying artificial
atom (pseudospin) interacting with a bosonic mode stored in a microwave
resonator. Besides observing abrupt changes in the spin-boson entanglement
evolution and bifurcation transition in quantum Rabi splitting, we demonstrate
super-sensitive quantum sensing by mapping the observable of interest to a
hitherto unobserved -manifested entanglement evolution. These
results pave the way for exploring non-Hermitian entanglement dynamics and
-enhanced quantum sensing empowered by nonclassical correlations.Comment: 25 pages, 19 figure
Emergent Schr\"{o}dinger cat states during superradiant phase transitions
Superradiant phase transitions (SPTs) are important for understanding
light-matter interactions at the quantum level [1, 2], and play a central role
in criticality-enhanced quantum sensing [3]. So far, SPTs have been observed in
driven-dissipative systems [4-9], but the emergent light fields did not show
any nonclassical characteristic due to the presence of strong dissipation. Here
we report an experimental demonstration of the SPT featuring the emergence of a
highly nonclassical photonic field, realized with a resonator coupled to a
superconducting qubit, implementing the quantum Rabi model [10, 11]. We fully
characterize the light-matter state by Wigner matrix tomography. The measured
matrix elements exhibit quantum interference intrinsic of a photonic
Schr\"{o}dinger cat state [12], and reveal light-matter entanglement. Besides
their fundamental importance, these hitherto unobserved emergent quantum
phenomena are useful for quantum metrology and fault-tolerant quantum
computation.Comment: 19 pages, 14 figures, 2 table
Experimental study of THGEM detector with mini-rim
The gas gain and energy resolution of single and double THGEM detectors
(5{\times}5cm2 effective area) with mini-rims (rim is less than 10{\mu}m) were
studied. The maximum gain can reach 5{\times}103 and 2{\times}105 for single
and double THGEM respectively, while the energy resolution of 5.9 keV X-ray
varied from 18% to 28% for both single and double THGEM detectors of different
hole sizes and thicknesses.All the experiments were investigated in mixture of
noble gases(argon,neon) and small content of other gases(iso-butane,methane) at
atmospheric pressure.Comment: 4pages,6figures, it has been submitted to Chinese Physics
Regulating the Coordination Environment of Mesopore‐Confined Single Atoms from Metalloprotein‐MOFs for Highly Efficient Biocatalysis (Adv. Mater. 44/2022)
Landauer transport model for Hawking radiation from a Reissner-Nordstrom black hole
The recent work of Nation et al in which Hawking radiation energy and entropy
flow from a black hole can be regarded as a one-dimensional (1D) Landauer
transport process is extended to the case of a Reissner-Nordstrom (RN) black
hole. It is found that the flow of charge current can also be transported via a
1D quantum channel except the current of Hawking radiation. The maximum entropy
current, which is shown to be particle statistics independence, is also
obtained
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