Theory of cavity ring-up spectroscopy

Cavity ring-up spectroscopy (CRUS) provides an advanced technique to sense ultrafast phenomena, but there is no thorough discussion on its theory. Here we give a detailed theoretical analysis of CRUS with and without modal coupling, and present exact analytical expressions for the normalized transmission, which are very simple under certain reasonable conditions. Our results provide a solid theoretical basis for the applications of CRUS.Comment: 6 pages, 2 figure

UU independent eigenstates of Hubbard model

Two-dimensional Hubbard model is very important in condensed matter physics. However it has not been resolved though it has been proposed for more than 50 years. We give several methods to construct eigenstates of the model that are independent of the on-site interaction strength $U$

Entanglement fidelity of the standard quantum teleportation channel

We consider the standard quantum teleportation protocol where a general bipartite state is used as entanglement resource. We use the entanglement fidelity to describe how well the standard quantum teleportation channel transmits quantum entanglement and give a simple expression for the entanglement fidelity when it is averaged on all input states.Comment: 3 page

Multi-Label Image Recognition with Graph Convolutional Networks

The task of multi-label image recognition is to predict a set of object labels that present in an image. As objects normally co-occur in an image, it is desirable to model the label dependencies to improve the recognition performance. To capture and explore such important dependencies, we propose a multi-label classification model based on Graph Convolutional Network (GCN). The model builds a directed graph over the object labels, where each node (label) is represented by word embeddings of a label, and GCN is learned to map this label graph into a set of inter-dependent object classifiers. These classifiers are applied to the image descriptors extracted by another sub-net, enabling the whole network to be end-to-end trainable. Furthermore, we propose a novel re-weighted scheme to create an effective label correlation matrix to guide information propagation among the nodes in GCN. Experiments on two multi-label image recognition datasets show that our approach obviously outperforms other existing state-of-the-art methods. In addition, visualization analyses reveal that the classifiers learned by our model maintain meaningful semantic topology.Comment: To appear at CVPR 2019 (Source codes have been released on https://github.com/chenzhaomin123/ML_GCN

Weak measurement with a coherent state pointer and its implementation in optomechanical system

Weak measurement with a coherent state pointer and in combination with an orthogonal postselection can lead to a surprising amplification effect, and we give a fire-new physical mechanism about the weak measurement in order to understand this effect. Moreover, this physical mechanism is a general result and based on it, we present a scheme of optomechanical system to implement weak measurement amplification on an orthogonal postselection

Weak measurement amplification in optomechanics via a squeezed coherent state pointer

We present a scheme for achieving amplification of the displacement of the mirror in optomechanical cavity using single-photon postselection where the mirror is initially prepared in squeezed coherent state. The amplification depends on the enhanced fluctuations of the squeezed coherent state, and it is is caused by the noncommutativity of quantum mechanics relying on the squeezed coherent state, which can not be explained by the standard weak measurement [1,25].Comment: arXiv admin note: substantial text overlap with arXiv:1509.0062

Ground State Properties of Spin-Orbit Coupled Bose Gases for Arbitrary Interactions

We develop a field integral formalism to study spin-orbit-coupled (SOC) Bose gases with arbitrary interspecies interaction. We identify various features arising from the interplay of SOC and interspecies interaction, including a roton minimum in the excitation spectrum and dual effects of SOC on ground-state energies depending on interspecies interactions. Counterintuitively, we find that at low interspecies interaction the SOC stabilizes the system by suppressing the quantum depletion. We show that the static structure factor is immune to the SOC in the phase space where time-reversal symmetry is preserved. Furthermore, we present an alternate way of studying phase fluctuations of the system.Comment: 5 pages, 4 figure

Entanglement charge of thermal states

Entanglement charge is an operational measure to quantify nonlocalities in ensembles consisting of bipartite quantum states. Here we generalize this nonlocality measure to single bipartite quantum states. As an example, we analyze the entanglement charges of some thermal states of two-qubit systems and show how they depend on the temperature and the system parameters in an analytical way.Comment: 4 pages, 3 figure

Enhancement of steady-state bosonic squeezing and entanglement in a dissipative optomechanical system

We systematically study the influence of amplitude modulation on the steady-state bosonic squeezing and entanglement in a dissipative three-mode optomechanical system, where a vibrational mode of the membrane is coupled to the left and right cavity modes via the radiation pressure. Numerical simulation results show that the steady-state bosonic squeezing and entanglement can be significantly enhanced by periodically modulated external laser driving either or both ends of the cavity. Remarkably, the fact that as long as one periodically modulated external laser driving either end of the cavities is sufficient to enhance the squeezing and entanglement is convenient for actual experiment, whose cost is that required modulation period number for achieving system stability is more. In addition, we numerically confirm the analytical prediction for optimal modulation frequency and discuss the corresponding physical mechanism.Comment: 25 pages, 8 figures, accepted for publication in Optics Expres

Searching for lepton flavor violating decays tau to Pl in Minimal R-symmetric Supersymmetric Standard Model

We analyze the lepton flavor violating decays $\tau\rightarrow Pl$ ($P=\pi,\eta,\eta';\;l=e,\mu$) in the scenario of the minimal R-symmetric supersymmetric standard model. The prediction on the branching ratios BR$(\tau\rightarrow P e)$ and BR$(\tau\rightarrow P \mu)$ is affected by the mass insertion parameters $\delta^{13}$ and $\delta^{23}$, respectively. These parameters are constrained by the experimental bounds on the branching ratios BR($\tau\rightarrow e (\mu) \gamma$) and BR($\tau\rightarrow 3e(\mu)$). The result shows $Z$ penguin dominates the prediction on BR($\tau\rightarrow Pl$) in a large region of the parameter space. The branching ratios for BR($\tau\rightarrow Pl$) are predicted to be, at least, five orders of magnitude smaller than present experimental bounds and three orders of magnitude smaller than future experimental sensitivities.Comment: 19 pages, 9 figures. arXiv admin note: text overlap with arXiv:2004.1226