51 research outputs found
Enhanced coherent light-matter interaction and room-temperature quantum yield of plasmonic resonances engineered by a chiral exceptional point
Strong dissipation of plasmonic resonances is detrimental to quantum
manipulation. To enhance the quantum coherence, we propose to tailor the local
density of states (LDOS) of plasmonic resonances by integrating with a photonic
cavity operating at a chiral exceptional point (CEP), where the phase of light
field can offer a new degree of freedom to flexibly manipulate the quantum
states. A quantized few-mode theory is employed to reveal that the LDOS of the
proposed hybrid cavity can evolve into sub-Lorentzian lineshape, with
order-of-magnitude linewidth narrowing and additionally a maximum of eightfold
enhancement compared to the usual plasmonic-photonic cavity without CEP. This
results in the enhanced coherent light-matter interaction accompanied by the
reduced dissipation of polaritonic states. Furthermore, a scattering theory
based on eigenmode decomposition is present to elucidate two mechanisms
responsible for the significant improvement of quantum yield at CEP, the
reduction of plasmonic absorption by the Fano interference and the enhancement
of cavity radiation through the superscattering. Importantly, we find the
latter allows achieving a near-unity quantum yield at room temperature; in
return, high quantum yield is beneficial to experimentally verify the enhanced
LDOS at CEP by measuring the fluorescence lifetime of a quantum emitter.
Therefore, our work demonstrates that the plasmonic resonances in
CEP-engineered environment can serve as a promising platform for exploring the
quantum states control by virtue of the non-Hermiticity of open optical
resonators and building the high-performance quantum devices for sensing,
spectroscopy, quantum information processing and quantum computing.Comment: 20 pages,9 figure
21 cm foreground removal using AI and frequency-difference technique
The deep learning technique has been employed in removing foreground
contaminants from 21 cm intensity mapping, but its effectiveness is limited by
the large dynamic range of the foreground amplitude. In this study, we develop
a novel foreground removal technique grounded in U-Net networks. The essence of
this technique lies in introducing an innovative data preprocessing step
specifically, utilizing the temperature difference between neighboring
frequency bands as input, which can substantially reduce the dynamic range of
foreground amplitudes by approximately two orders of magnitude. This reduction
proves to be highly advantageous for the U-Net foreground removal. We observe
that the HI signal can be reliably recovered, as indicated by the
cross-correlation power spectra showing unity agreement at the scale of Mpc in the absence of instrumental effects. Moreover, accounting for
the systematic beam effects, our reconstruction displays consistent
auto-correlation and cross-correlation power spectrum ratios at the
level across scales Mpc, with only a 10% reduction
observed in the cross-correlation power spectrum at Mpc. The
effects of redshift-space distortion are also reconstructed successfully, as
evidenced by the quadrupole power spectra matching. In comparison, our method
outperforms the traditional Principal Component Analysis method, which derived
cross-correlation ratios are underestimated by around 75%. We simulated various
white noise levels in the map and found that the mean cross-correlation ratio
when the level of the thermal noise is
smaller than or equal to that of the HI signal. We conclude that the proposed
frequency-difference technique can significantly enhance network performance by
reducing the amplitude range of foregrounds and aiding in the prevention of HI
loss.Comment: 18 pages, 16 figure
Future Gradient Descent for Adapting the Temporal Shifting Data Distribution in Online Recommendation Systems
One of the key challenges of learning an online recommendation model is the
temporal domain shift, which causes the mismatch between the training and
testing data distribution and hence domain generalization error. To overcome,
we propose to learn a meta future gradient generator that forecasts the
gradient information of the future data distribution for training so that the
recommendation model can be trained as if we were able to look ahead at the
future of its deployment. Compared with Batch Update, a widely used paradigm,
our theory suggests that the proposed algorithm achieves smaller temporal
domain generalization error measured by a gradient variation term in a local
regret. We demonstrate the empirical advantage by comparing with various
representative baselines
Multi-configurational nature of electron correlation within nitrogen vacancy centers in diamond
Diamond is a solid-state platform to develop quantum technologies, but it has
been a long-standing problem that the current understanding of quantum states
in diamond is mostly limited to single-electron pictures. Here, we combine the
full configuration interaction quantum Monte Carlo method and the
density-matrix functional embedding theory, to achieve unprecedented accuracy
in describing the many-body quantum states of nitrogen vacancy (NV) centers in
diamond. More than 30 electrons and 130 molecular orbitals are correlated,
which reveals the multi-configurational wavefunction of the many-body quantum
states in diamond. The multi-configurational description explains puzzling
experimental measurements in intersystem crossing and charge state transition
in NV centers in diamond. The calculations not only reproduce the available
experimental measurements of the energy gaps between quantum states but also
provide new benchmarks for states that are still subject to considerable
uncertainty. This study highlights the importance of multi-configurational
wavefunction in the many-body quantum states in solids
Association between investigator-measured body-mass index and colorectal adenoma: a systematic review and meta-analysis of 168,201 subjects
The objective of this meta-analysis is to evaluate the odds of colorectal adenoma (CRA) in colorectal cancer screening participants with different body mass index (BMI) levels, and examine if this association was different according to gender and ethnicity. The EMBASE and MEDLINE were searched to enroll high quality observational studies that examined the association between investigator-measured BMI and colonoscopy-diagnosed CRA. Data were independently extracted by two reviewers. A random-effects meta-analysis was conducted to estimate the summary odds ratio (SOR) for the association between BMI and CRA. The Cochran’s Q statistic and I2 analyses were used to assess the heterogeneity. A total of 17 studies (168,201 subjects) were included. When compared with subjects having BMI < 25, individuals with BMI 25–30 had significantly higher risk of CRA (SOR 1.44, 95% CI 1.30–1.61; I2 = 43.0%). Subjects with BMI ≥ 30 had similarly higher risk of CRA (SOR 1.42, 95% CI 1.24–1.63; I2 = 18.5%). The heterogeneity was mild to moderate among studies. The associations were significantly higher than estimates by previous meta-analyses. There was no publication bias detected (Egger’s regression test, p = 0.584). Subgroup analysis showed that the magnitude of association was significantly higher in female than male subjects (SOR 1.43, 95% CI 1.30–1.58 vs. SOR 1.16, 95% CI 1.07–1.24; different among different ethnic groups (SOR 1.72, 1.44 and 0.88 in White, Asians and Africans, respectively) being insignificant in Africans; and no difference exists among different study designs. In summary, the risk conferred by BMI for CRA was significantly higher than that reported previously. These findings bear implications in CRA risk estimation
Discovery of Diverse Rodent and Bat Pestiviruses With Distinct Genomic and Phylogenetic Characteristics in Several Chinese Provinces
Bats and rodents are widely distributed worldwide and can be native or intermediate reservoirs of many important zoonotic viruses. Pestiviruses are a group of virus species of the genus Pestivirus under the family Flaviviridae that can infect a wide variety of artiodactylous hosts, including swine and ruminants. Two classic types of pestiviruses, bovine viral diarrhea virus and classical swine fever virus, are important causative agents of mild-to-severe disease in bovine and swine hosts, respectively, and cause tremendous economic losses in these industries. Recent reports revealed that bats and rodents could also act as natural hosts of pestiviruses and an atypical porcine pestivirus, which cause disease in piglets, showed a close genetic relationship with a specific bat pestivirus, RaPestV-1. This study aimed to describe the detection and characterization of novel pestiviruses from bats and rodents in different locations by analyzing the available bat and rodent virome data from throughout China. Two bat pestivirus species and four rodent pestivirus species that are distinct from other known viruses were identified and sequenced. These viruses were identified from two bat species and four rodent species in different Chinese provinces. There were two distinct lineages present in these viruses, that differ from artiodactylous pestivirus. These findings expand our understanding of the genetic diversity of pestiviruses in bats and rodents and suggest the presence of a diverse set of pestiviruses in non-artiodactylous hosts. This study may provide new insight for the prevention of future viral disease outbreaks originating from bats and rodents
ST Segment Extraction from Exercise ECG Signal Based on EMD and Wavelet Transform
Myocardial ischemia is always characterized by the changes in ST complex. But ischemia is not obvious at rest. Only in the state of exercise, abnormal ST will appear. The signal of ST is susceptible to noise interference which causes the inaccuracy of the ST segment detection. Combining the advantages of empirical mode decomposition (EMD), the paper proposes a modified threshold method to filter a serious of noise from exercise ECG. Extracted from the ECG feature, it includes ST segment detection, with wavelet transform. In the end, the method is tested with synthetic exercise data and real exercise ECG data. The results of ST segment detection are accurate and this method can be applied in practical exercise
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