6,068 research outputs found
Fast geometric gate operation of superconducting charge qubits in circuit QED
A scheme for coupling superconducting charge qubits via a one-dimensional
superconducting transmission line resonator is proposed. The qubits are working
at their optimal points, where they are immune to the charge noise and possess
long decoherence time. Analysis on the dynamical time evolution of the
interaction is presented, which is shown to be insensitive to the initial state
of the resonator field. This scheme enables fast gate operation and is readily
scalable to multiqubit scenario
Quantum simulation of exotic PT-invariant topological nodal loop bands with ultracold atoms in an optical lattice
Since the well-known PT symmetry has its fundamental significance and
implication in physics, where PT denotes the combined operation of
space-inversion P and time-reversal T, it is extremely important and intriguing
to completely classify exotic PT-invariant topological metals and to physically
realize them. Here we, for the first time, establish a rigorous classification
of topological metals that are protected by the PT symmetry using KO-theory. As
a physically realistic example, a PT-invariant nodal loop (NL) model in a 3D
Brillouin zone is constructed, whose topological stability is revealed through
its PT-symmetry-protected nontrivial Z2 topological charge. Based on these
exact results, we propose an experimental scheme to realize and to detect
tunable PT-invariant topological NL states with ultracold atoms in an optical
lattice, in which atoms with two hyperfine spin states are loaded in a
spin-dependent 3D OL and two pairs of Raman lasers are used to create
out-of-plane spin-flip hopping with site-dependent phase. Such a realistic
cold-atom setup can yield topological NL states, having a tunable ring-shaped
band-touching line with the two-fold degeneracy in the bulk spectrum and
non-trivial surface states. The states are actually protected by the combined
PT symmetry even in the absence of both P and T symmetries, and are
characterized by a Z2-type invariant (a quantized Berry phase). Remarkably, we
demonstrate with numerical simulations that (i) the characteristic NL can be
detected by measuring the atomic transfer fractions in a Bloch-Zener
oscillation; (ii) the topological invariant may be measured based on the
time-of-flight imaging; and (iii) the surface states may be probed through
Bragg spectroscopy. The present proposal for realizing topological NL states in
cold atom systems may provide a unique experimental platform for exploring
exotic PT-invariant topological physics.Comment: 11 pages, 6 figures; accepted for publication in Phys. Rev.
High fidelity quantum state transfer in electromechanical systems with intermediate coupling
published_or_final_versio
GAN-Based Differential Private Image Privacy Protection Framework for the Internet of Multimedia Things.
With the development of the Internet of Multimedia Things (IoMT), an increasing amount of image data is collected by various multimedia devices, such as smartphones, cameras, and drones. This massive number of images are widely used in each field of IoMT, which presents substantial challenges for privacy preservation. In this paper, we propose a new image privacy protection framework in an effort to protect the sensitive personal information contained in images collected by IoMT devices. We aim to use deep neural network techniques to identify the privacy-sensitive content in images, and then protect it with the synthetic content generated by generative adversarial networks (GANs) with differential privacy (DP). Our experiment results show that the proposed framework can effectively protect users' privacy while maintaining image utility
Genome-scale analysis and comparison of gene expression profiles in developing and germinated pollen in Oryza sativa
<p>Abstract</p> <p>Background</p> <p>Pollen development from the microspore involves a series of coordinated cellular events, and the resulting mature pollen has a specialized function to quickly germinate, produce a polar-growth pollen tube derived from the vegetative cell, and deliver two sperm cells into the embryo sac for double fertilization. The gene expression profiles of developing and germinated pollen have been characterised by use of the eudicot model plant <it>Arabidopsis</it>. Rice, one of the most important cereal crops, has been used as an excellent monocot model. A comprehensive analysis of transcriptome profiles of developing and germinated pollen in rice is important to understand the conserved and diverse mechanism underlying pollen development and germination in eudicots and monocots.</p> <p>Results</p> <p>We used Affymetrix GeneChip<sup>® </sup>Rice Genome Array to comprehensively analyzed the dynamic changes in the transcriptomes of rice pollen at five sequential developmental stages from microspores to germinated pollen. Among the 51,279 transcripts on the array, we found 25,062 pollen-preferential transcripts, among which 2,203 were development stage-enriched. The diversity of transcripts decreased greatly from microspores to mature and germinated pollen, whereas the number of stage-enriched transcripts displayed a "U-type" change, with the lowest at the bicellular pollen stage; and a transition of overrepresented stage-enriched transcript groups associated with different functional categories, which indicates a shift in gene expression program at the bicellular pollen stage. About 54% of the now-annotated rice F-box protein genes were expressed preferentially in pollen. The transcriptome profile of germinated pollen was significantly and positively correlated with that of mature pollen. Analysis of expression profiles and coexpressed features of the pollen-preferential transcripts related to cell cycle, transcription, the ubiquitin/26S proteasome system, phytohormone signalling, the kinase system and defense/stress response revealed five expression patterns, which are compatible with changes in major cellular events during pollen development and germination. A comparison of pollen transcriptomes between rice and <it>Arabidopsis </it>revealed that 56.6% of the rice pollen preferential genes had homologs in <it>Arabidopsis </it>genome, but 63.4% of these homologs were expressed, with a small proportion being expressed preferentially, in <it>Arabidopsis </it>pollen. Rice and <it>Arabidopsis </it>pollen had non-conservative transcription factors each.</p> <p>Conclusions</p> <p>Our results demonstrated that rice pollen expressed a set of reduced but specific transcripts in comparison with vegetative tissues, and the number of stage-enriched transcripts displayed a "U-type" change during pollen development, with the lowest at the bicellular pollen stage. These features are conserved in rice and <it>Arabidopsis</it>. The shift in gene expression program at the bicellular pollen stage may be important to the transition from earlier cell division to later pollen maturity. Pollen at maturity pre-synthesized transcripts needed for germination and early pollen tube growth. The transcription regulation associated with pollen development would have divergence between the two species. Our results also provide novel insights into the molecular program and key components of the regulatory network regulating pollen development and germination.</p
Continuum of Bound States in a Non-Hermitian Model
In a Hermitian system, bound states must have quantized energies, whereas
extended states can form a continuum. We demonstrate how this principle fails
for non-Hermitian systems, by analyzing non-Hermitian continuous Hamiltonians
with an imaginary momentum and Landau-type vector potential. The eigenstates,
which we call ``continuum Landau modes'' (CLMs), have gaussian spatial
envelopes and form a continuum filling the complex energy plane. We present
experimentally-realizable 1D and 2D lattice models that can be used to study
CLMs; the lattice eigenstates are localized and have other features that are
the same as in the continuous model. One of these lattices can serve as a
rainbow trap, whereby the response to an excitation is concentrated at a
position proportional to the frequency. Another lattice can act a wave funnel,
concentrating an input excitation onto a boundary over a wide frequency
bandwidth. Unlike recent funneling schemes based on the non-Hermitian skin
effect, this requires only a simple lattice design without nonreciprocal
couplings
Anomalous Floquet non-Hermitian skin effect in a ring resonator lattice
We present a one-dimensional coupled ring resonator lattice exhibiting a
variant of the non- Hermitian skin effect (NHSE) that we call the anomalous
Floquet NHSE. Unlike existing approaches to achieving the NHSE by engineering
gain and loss on different ring segments, our design uses fixed on-site gain or
loss in each ring. The anomalous Floquet NHSE is marked by the existence of
skin modes at every value of the Floquet quasienergy, allowing for broadband
asymmetric transmission. Varying the gain/loss induces a non-Hermitian
topological phase transition, reversing the localization direction of the skin
modes. An experimental implementation in an acoustic lattice yields good
agreement with theoretical predictions, with a very broad relative bandwidth of
around 40%.Comment: 7 pages, 3 figure
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