193 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
Scientists' bounded mobility on the epistemic landscape
Despite persistent efforts in revealing the temporal patterns in scientific
careers, little attention has been paid to the spatial patterns of scientific
activities in the knowledge space. Here, drawing on millions of papers in six
disciplines, we consider scientists' publication sequence as "walks" on the
quantifiable epistemic landscape constructed from large-scale bibliometric
corpora by combining embedding and manifold learning algorithms, aiming to
reveal the individual research topic dynamics and association between research
radius with academic performance, along their careers. Intuitively, the
visualization shows the localized and bounded nature of mobile trajectories. We
further find that the distributions of scientists' transition radius and
transition pace are both left-skewed compared with the results of controlled
experiments. Then, we observe the mixed exploration and exploitation pattern
and the corresponding strategic trade-off in the research transition, where
scientists both deepen their previous research with frequency bias and explore
new research with knowledge proximity bias. We further develop a bounded
exploration-exploitation (BEE) model to reproduce the observed patterns.
Moreover, the association between scientists' research radius and academic
performance shows that extensive exploration will not lead to a sustained
increase in academic output but a decrease in impact. In addition, we also note
that disruptive findings are more derived from an extensive transition, whereas
there is a saturation in this association. Our study contributes to the
comprehension of the mobility patterns of scientists in the knowledge space,
thereby providing significant implications for the development of scientific
policy-making.Comment: article paper, 47 pages, 29 figures, 4 table
Understanding and Improving Recurrent Networks for Human Activity Recognition by Continuous Attention
Deep neural networks, including recurrent networks, have been successfully
applied to human activity recognition. Unfortunately, the final representation
learned by recurrent networks might encode some noise (irrelevant signal
components, unimportant sensor modalities, etc.). Besides, it is difficult to
interpret the recurrent networks to gain insight into the models' behavior. To
address these issues, we propose two attention models for human activity
recognition: temporal attention and sensor attention. These two mechanisms
adaptively focus on important signals and sensor modalities. To further improve
the understandability and mean F1 score, we add continuity constraints,
considering that continuous sensor signals are more robust than discrete ones.
We evaluate the approaches on three datasets and obtain state-of-the-art
results. Furthermore, qualitative analysis shows that the attention learned by
the models agree well with human intuition.Comment: 8 pages. published in The International Symposium on Wearable
Computers (ISWC) 201
AuE-IPA: An AU Engagement Based Infant Pain Assessment Method
Recent studies have found that pain in infancy has a significant impact on
infant development, including psychological problems, possible brain injury,
and pain sensitivity in adulthood. However, due to the lack of specialists and
the fact that infants are unable to express verbally their experience of pain,
it is difficult to assess infant pain. Most existing infant pain assessment
systems directly apply adult methods to infants ignoring the differences
between infant expressions and adult expressions. Meanwhile, as the study of
facial action coding system continues to advance, the use of action units (AUs)
opens up new possibilities for expression recognition and pain assessment. In
this paper, a novel AuE-IPA method is proposed for assessing infant pain by
leveraging different engagement levels of AUs. First, different engagement
levels of AUs in infant pain are revealed, by analyzing the class activation
map of an end-to-end pain assessment model. The intensities of top-engaged AUs
are then used in a regression model for achieving automatic infant pain
assessment. The model proposed is trained and experimented on YouTube
Immunization dataset, YouTube Blood Test dataset, and iCOPEVid dataset. The
experimental results show that our AuE-IPA method is more applicable to infants
and possesses stronger generalization ability than end-to-end assessment model
and the classic PSPI metric
Topologically protected subradiant cavity polaritons through linewidth narrowing enabled by dissipationless edge states
Cavity polaritons derived from the strong light-matter interaction at the
quantum level provide a basis for efficient manipulation of quantum states via
cavity field. Polaritons with narrow linewidth and long lifetime are appealing
in applications such as quantum sensing and storage. Here, we propose a
prototypical arrangement to implement a whispering-gallery-mode resonator with
topological mirror moulded by one-dimensional atom array, which allows to boost
the lifetime of cavity polaritons over an order of magnitude. This considerable
enhancement attributes to the coupling of polaritonic states to dissipationless
edge states protected by the topological bandgap of atom array that suppresses
the leakage of cavity modes. When exceeding the width of Rabi splitting,
topological bandgap can further reduce the dissipation from polaritonic states
to bulk states of atom array, giving arise to subradiant cavity polaritons with
extremely sharp linewidth. The resultant Rabi oscillation decays with a rate
even below the free-space decay of a single quantum emitter. Inheriting from
the topologically protected properties of edge states, the subradiance of
cavity polaritons can be preserved in the disordered atom mirror with moderate
perturbations involving the atomic frequency, interaction strengths and
location. Our work opens up a new paradigm of topology-engineered quantum
states with robust quantum coherence for future applications in quantum
computing and network.Comment: 19 pages,8 figure
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