Generative Feature Replay with Orthogonal Weight Modification for Continual Learning

The ability of intelligent agents to learn and remember multiple tasks sequentially is crucial to achieving artificial general intelligence. Many continual learning (CL) methods have been proposed to overcome catastrophic forgetting which results from non i.i.d data in the sequential learning of neural networks. In this paper we focus on class incremental learning, a challenging CL scenario. For this scenario, generative replay is a promising strategy which generates and replays pseudo data for previous tasks to alleviate catastrophic forgetting. However, it is hard to train a generative model continually for relatively complex data. Based on recently proposed orthogonal weight modification (OWM) algorithm which can approximately keep previously learned feature invariant when learning new tasks, we propose to 1) replay penultimate layer feature with a generative model; 2) leverage a self-supervised auxiliary task to further enhance the stability of feature. Empirical results on several datasets show our method always achieves substantial improvement over powerful OWM while conventional generative replay always results in a negative effect. Meanwhile our method beats several strong baselines including one based on real data storage. In addition, we conduct experiments to study why our method is effective.Comment: Under Revie

Estimating the production rates of D-wave charmed mesons via the semileptonic decays of bottom mesons

In this work, using the covariant light front approach with conventional vertex functions, we estimate the production rates of $D$-wave charmed/charmed-strange mesons via $B_{(s)}$ semileptonic decays. Due to these calculated considerable production rates, it is possible to experimentally search for $D$-wave charmed/charmed-strange mesons via the semileptonic decays, which may provide extra approach to explore $D$-wave charmed/charmed-strange mesons.Comment: 25 pages, 6 figures and 4 table

Symmetry protected topological Luttinger liquids and the phase transition between them

We show that a doped spin-1/2 ladder with antiferromagnetic intra-chain and ferromagnetic inter-chain coupling is a symmetry protected topologically non-trivial Luttinger liquid. Turning on a large easy-plane spin anisotropy drives the system to a topologically-trivial Luttinger liquid. Both phases have full spin gaps and exhibit power-law superconducting pair correlation. The Cooper pair symmetry is singlet $d_{xy}$ in the non-trivial phase and triplet $S_z=0$ in the trivial phase. The topologically non-trivial Luttinger liquid exhibits gapless spin excitations in the presence of a boundary, and it has no non-interacting or mean-field theory analog even when the fluctuating phase in the charge sector is pinned. As a function of the strength of spin anisotropy there is a topological phase transition upon which the spin gap closes. We speculate these Luttinger liquids are relevant to the superconductivity in metalized integer spin ladders or chains.Comment: 5.2 pages, 4 figures + 2.8 pages supplemental material

Unified Fano-like interference picture for charmonium-like states Y(4008)Y(4008), Y(4260)Y(4260) and Y(4360)Y(4360)

We propose that the unified Fano-like interference picture applies to $e^+e^-\to \pi^+\pi^- J/\psi$ and $e^+e^-\to \pi^+\pi^- \psi(3686)$, where $Y(4260)$ and $Y(4360)$ are observed, respectively, to provide a reasonable interpretation of the asymmetric lines hapes of $Y(4260)$ and $Y(4360)$ structures. Moreover, the Fano-like interference induces an extra broad structure $Y(4008)$ in $e^+e^-\to \pi^+\pi^- J/\psi$ as a companion peak to $Y(4260)$. Three charmonium-like states $Y(4008)$, $Y(4260)$ and $Y(4360)$ observed in $e^+e^-$ annihilation processes are not genuine resonances. Under this scenario, it is well explained why $Y(4008)$, $Y(4260)$ and $Y(4360)$ are absent in the experimental data of the $R$ value scan and missing in open-charm decay channels. Although the present work presents a typical application of the Fano-like interference in particle physics at the lower energy region, we have reason to believe that the Fano-like phenomena may exist in other processes such as $e^+e^-\to \pi^+\pi^-\psi(3770)$ and $e^+e^-\to K^+K^- J/\psi$, which will be accessible at BESIII and forthcoming BelleII.Comment: 5 pages, 4 figures and 1 table. More discussions and references added. Accepted by PR

Observation of Mollow triplet with metastability exchange collisions in 3He atoms

We study the dressed states of 3He atoms and experimentally observe the Mollow triplet (MT) induced with an ultra-low-frequency (ULF) oscillating magnetic field as low as 4 Hz. The ULF MT signatures from the ground states of 3He atoms are transferred to the metastable states by metastability-exchange collisions (MECs) and measured optically, which demonstrates 2 s coherence time in the dressed ground states. The result shows the possibility of ULF magnetic field amplitude measurement and a new scheme for optical frequency modulation

Light Source Monitoring in Quantum Key Distribution with Single Photon Detector at Room Temperature

Photon number resolving monitoring is a practical light source monitoring scheme in QKD systems, which reduces the impacts from untrusted sources effectively. This scheme requires a single photon detector, normally working at low temperature to suppress its dark count rate. In this paper, we use a room-temperature detector and show that the dark count rate is irrelevant to the monitoring performance in our scheme, which can sufficiently relax requirements on the detector's working conditions as well as integration complexity, and this would be highly demanded for practical systems. Furthermore, influences of parameter drifts at room temperature are analyzed, and the monitoring scheme is testified in a real QKD system

Observation of Mollow quintuplet in F=3/2 hyperfine structure state of 3He atomic cell

We experimentally observed the Mollow quintuplet (MQ) in F=3/2 hyperfine structure state of 3He atoms. The metastability-exchange collisions (MECs) transfer the Mollow Triplet (MT) from the ground states of 3He atoms to the metastable states, and the MQ is demonstrated by four Zeeman levels of F=3/2 hyperfine states with linearly polarized light. The similar effect also achieves in the mixture cell of 3He and 4He.Comment: 4 pages, 6 figures. arXiv admin note: text overlap with arXiv:1810.1177

Glueball Masses in QCD_3

We discuss how to extract the spectroscopy of quantum chromodynamics (QCD) in the pure gauge sector from the Hamiltonian lattice field theory approach. The recently developed truncated eigenvalue equation method is applied to the estimation of the scalar glueball $0^{++}$ and $0^{--}$ masses in the (2+1)-dimensional case. These masses reach the constant values in a scaling region as required by the renormalizability.Comment: 8 pages plus 2 figures, encoded with uufiles

Non-Gaussian postselection and virtual photon subtraction in continuous-variable quantum key distribution

Photon subtraction can enhance the performance of continuous-variable quantum key distribution (CV QKD). However, the enhancement effect will be reduced by the imperfections of practical devices, especially the limited efficiency of a single-photon detector. In this paper, we propose a non-Gaussian postselection method to emulate the photon substraction used in coherent-state CV QKD protocols. The virtual photon subtraction not only can avoid the complexity and imperfections of a practical photon-subtraction operation, which extends the secure transmission distance as the ideal case does, but also can be adjusted flexibly according to the channel parameters to optimize the performance. Furthermore, our preliminary tests on the information reconciliation suggest that in the low signal-to-noise ratio regime, the performance of reconciliating the postselected non-Gaussian data is better than that of the Gaussian data, which implies the feasibility of implementing this method practically.Comment: 10 pages, 6 figure

A new one-dimensional variable frequency photonic crystals

In this paper, we have firstly proposed a new one-dimensional variable frequency photonic crystals (VFPCs). We have calculated the transmissivity and the electronic field distribution of VFPCs and compare them with the conventional PCs, and obtained some new results, which should be help to design a new type optical devices, and the two-dimensional and three-dimensional VFPCs can be studied further.Comment: arXiv admin note: text overlap with arXiv:1301.6109 by other author