Hierarchical Pooling Structure for Weakly Labeled Sound Event Detection

Sound event detection with weakly labeled data is considered as a problem of multi-instance learning. And the choice of pooling function is the key to solving this problem. In this paper, we proposed a hierarchical pooling structure to improve the performance of weakly labeled sound event detection system. Proposed pooling structure has made remarkable improvements on three types of pooling function without adding any parameters. Moreover, our system has achieved competitive performance on Task 4 of Detection and Classification of Acoustic Scenes and Events (DCASE) 2017 Challenge using hierarchical pooling structure

SAM-GCNN: A Gated Convolutional Neural Network with Segment-Level Attention Mechanism for Home Activity Monitoring

In this paper, we propose a method for home activity monitoring. We demonstrate our model on dataset of Detection and Classification of Acoustic Scenes and Events (DCASE) 2018 Challenge Task 5. This task aims to classify multi-channel audios into one of the provided pre-defined classes. All of these classes are daily activities performed in a home environment. To tackle this task, we propose a gated convolutional neural network with segment-level attention mechanism (SAM-GCNN). The proposed framework is a convolutional model with two auxiliary modules: a gated convolutional neural network and a segment-level attention mechanism. Furthermore, we adopted model ensemble to enhance the capability of generalization of our model. We evaluated our work on the development dataset of DCASE 2018 Task 5 and achieved competitive performance, with a macro-averaged F-1 score increasing from 83.76% to 89.33%, compared with the convolutional baseline system.Comment: 6 pages, accepted by ISSPIT 201

More randomness from a prepare-and-measure scenario with independent devices

How to generate genuine quantum randomness from untrusted devices is an important problem in quantum information processing. Inspired by previous work on a self-testing quantum random number generator [T. Lunghi et al., Phys. Rev. Lett. 114, 150501 (2015)], we present a method to generate quantum randomness from a prepare-and-measure scenario with independent devices. In existing protocols, the quantum randomness depends only on a witness value (e.g., Clauser-Horne-Shimony-Holt value), which is calculated with the observed probabilities. Differently, here all the observed probabilities are directly used to calculate the min-entropy in our method. Through numerical simulation, we find that the min-entropy of our proposed scheme is higher than that in the previous work when a typical untrusted Bennett-Brassard 1984 (BB84) setup is used. Consequently, thanks to the proposed method, more genuine quantum random numbers may be obtained than before.Comment: 8 pages, 3 figure

Security of modified Ping-Pong protocol in noisy and lossy channel

The "Ping-Pong" (PP) protocol is a two-way quantum key protocol based on entanglement. In this protocol, Bob prepares one maximally entangled pair of qubits, and sends one qubit to Alice. Then, Alice performs some necessary operations on this qubit and sends it back to Bob. Although this protocol was proposed in 2002, its security in the noisy and lossy channel has not been proven. In this report, we add a simple and experimentally feasible modification to the original PP protocol, and prove the security of this modified PP protocol against collective attacks when the noisy and lossy channel is taken into account. Simulation results show that our protocol is practical.Comment: 7 pages, 2 figures, published in scientific report

Security of "Counterfactual Quantum Cryptography"

Recently, a "counterfactual" quantum key distribution scheme was proposed by Tae-Gon Noh [1]. In this scheme, two legitimate distant peers may share secret keys even when the information carriers are not traveled in the quantum channel. We find that this protocol is equivalent to an entanglement distillation protocol (EDP). According to this equivalence, a strict security proof and the asymptotic key bit rate are both obtained when perfect single photon source is applied and Trojan-horse attack can be detected. We also find that the security of this scheme is deeply related with not only the bit error rate but also the yields of photons. And our security proof may shed light on security of other two-way protocols.Comment: 5 pages, 1 figur

Thermodynamics of rotating Bose gases in a trap

Novel ground state properties of rotating Bose gases have been intensively studied in the context of neutral cold atoms. We investigate the rotating Bose gas in a trap from a thermodynamic perspective, taking the charged ideal Bose gas in magnetic field (which is equivalent to a neutral gas in a synthetic magnetic field) as an example. It is indicated that the Bose-Einstein condensation temperature is irrelevant to the magnetic field, conflicting with established intuition that the critical temperature decreases with the field increasing. The specific heat and Landau diamagnetization also exhibit intriguing behaviors. In contrast, we demonstrate that the condensation temperature for neutral Bose gases in a rotating frame drops to zero in the fast rotation limit, signaling a non-condensed quantum phase in the ground state.Comment: 4 pages, 1 figur

Chau-Wang-Wong17 Scheme Is Experimentally More Feasible Than The Six-State Scheme

Recently, Chau et al. [Phys. Rev. A 95, 022311 (2017)] reported a quantum-key-distribution (QKD) scheme using four-dimensional qudits. Surprisingly, as a function of the bit error rate of the raw key, the secret key rate of this scheme is equal to that of the (qubit-based) six-state scheme under one-way classical communication using ideal apparatus in the limit of arbitrarily long raw key length. Here we explain why this is the case in spite of the fact that these two schemes are not linearly related to each other. More importantly, we find that in terms of the four-dimensional dit error rate of the raw key, the Chau et al.'s scheme can tolerate up to 21.6% using one-way classical communications, which is better than the Sheridan and Scarani's scheme [Phys. Rev. A 82, 030301(R) (2010)]. In addition, we argue the experimental advantages of the Chau et al. implementation over the standard six-state scheme and report a corresponding proof-of-principle experiment using passive basis selection with decoy states. We also compare our experiment with the recent high secret key rate implementation of the Sheridan and Scarani's scheme by Islam et al. [Sci. Adv. \text{3}, e1701491].Comment: 8 pages, to appear in QI

Phase-encoded measurement device independent quantum key distribution with practical spontaneous parametric-down-conversion sources

Measurement-device-independent quantum key distribution (MDI-QKD) with weak coherent sources has been widely and meticulously analyzed. However, the analysis for MDI-QKD with spontaneous parametric-down-conversion sources (SPDCS) is incomplete. In this paper, by accounting for practical parameters of SPDCS with thermal distribution, we presents an investigation on the performances of MDI-QKD under the active three-intensity decoy protocol and the passive one-intensity decoy protocol respectively. Phase randomization, inherently prerequisite for decoy protocol, is taken into consideration for evaluating the overall quantum bit gain and quantum bit error rate. The numerical simulations show that MDI-QKD using SPDCS with practical decoy protocols can be demonstrated comparable to the asymptotical case with infinite decoy states and has apparent superiority both in transmission distance and key generation rate compared to the MDI-QKD using weak coherent sources. Our results also indicate that MDI-QKD using thermal distributed SPDCS with active three-intensity decoy protocol performs better than the one with passive one-intensity decoy protocol.Comment: 13 pages, 6 figure

Detection efficiency and noise in semi-device independent randomness extraction protocol

In this paper, we analyze several critical issues in semi-device independent quantum information processing protocol. In practical experimental realization randomness generation in that scenario is possible only if the efficiency of the detectors used is above a certain threshold. Our analysis shows that the critical detection efficiency is 0.7071 in the symmetric setup, while in the asymmetric setup if one of the bases has perfect critical detection efficiency then the other one can be arbitrarily close to 0. We also analyze the semi-device independent random number generation efficiency based on different averages of guessing probability. To generate more randomness, the proper averaging method should be applied. Its choice depends on the value of a certain dimension witness. More importantly, the general analytical relationship between the maximal average guessing probability and dimension witness is given

Monte Carlo study of thermal fluctuations and Fermi-arc formation in d-wave superconductors

From the perspective of thermal fluctuations, we investigate the pseudogap phenomena in underdoped high-temperature curpate superconductors. We present a local update Monte Carlo procedure based on the Green's function method to sample the fluctuating pairing field. The Chebyshev polynomial method is applied to calculate the single-particle spectral function directly and efficiently. The evolution of Fermi arcs as a function of temperature is studied by examining the spectral function at Fermi energy as well as the loss of spectral weight. Our results signify the importance of the vortex-like phase fluctuation on the formation of Fermi arcs.Comment: 9 pages, 3 figures. Figures redraw