arXiv subjects

Bing Chen

Publications and source records attributed to Bing Chen.

At least 55 records · Page 3Linked to original sources

arXiv2020

Resolving the low mass puzzle of $Λ_c(2940)^+$

For the long standing low mass puzzle of $Λ_c(2940)^+$, we propose an unquenched picture. Our calculation explicitly shows that the mass of the $Λ_c(2P,3/2^-)$ state can be lowered down to be consistent with the experimental data of $Λ_c(2940)^+$ by introducing the $D^*N$ channel contribution. Additionally, we give a semi-quantitative analysis to illustrate why the $Λ_c(2940)^+$ state has a narrow width. It means that the low mass puzzle of $Λ_c(2940)^+$ can be solved. What is more important is that we predict a mass inversion relation for the $2P$ $Λ_{c}^+$ states, i.e., the $Λ_c(2P,1/2^-)$ state is higher than the $Λ_c(2P,3/2^-)$, which is totally different from the result of conventional quenched quark model. It provides a criterion to test such an unquenched scenario for $Λ_c(2940)^+$. We expect the future experimental progress from the LHCb and Belle II.

hep-ph↗

arXiv2020

Bottomonium spectrum in the relativistic flux tube model

The bottomonium spectrum is far from being established. The structures of higher vector states, including the $Υ(10580)$, $Υ(10860)$, and $Υ(11020)$ states, are still in dispute. In addition, whether the $Υ(10750)$ signal which was recently observed by the Belle Collaboration is a normal $b\bar{b}$ state or not should be examined. Faced with such a situation, we carried out a systematic investigation of the bottomonium spectrum in the scheme of the relativistic flux tube (RFT) model. A Chew-Frautschi like formula was derived analytically for the spin average mass of bottomonium states. We further incorporated the spin-dependent interactions and obtained a complete bottomonium spectrum. We found that the most established bottomonium states can be explained in the RFT scheme. The $Υ(10750)$, $Υ(10860)$, and $Υ(11020)$ could be predominantly the $3^3D_1$, $5^3S_1$, and $4^3D_1$ states, respectively. Our predicted masses of $1F$ and $1G$ $b\bar{b}$ states are in agreement with the results given by the method of lattice QCD, which can be tested by experiments in future. We also compared the RFT model with the quark potential model in detail. The differences of these two kinds of models were discussed.

hep-ph↗

arXiv2020

Detecting dynamical quantum phase transition via out-of-time-order correlations in a solid-state quantum simulator

Quantum many body system in equilibrium can be effectively characterized using the framework of quantum statistical mechanics. However, nonequilibrium behaviour of quantum many body systems remains elusive, out of the range of such a well established framework. Experiments in quantum simulators are now opening up a route towards the generation of quantum states beyond this equilibrium paradigm. As an example in closed quantum many body systems, dynamical quantum phase transitions behave as phase transitions in time with physical quantities becoming nonanalytic at critical times, extending important principles such as universality to the nonequilibrium realm. Here, in solid state quantum simulator we develop and experimentally demonstrate that out-of-time-order correlators, a central concept to quantify quantum information scrambling and quantum chaos, can be used to dynamically detect nonoequilibrium phase transitions in the transverse field Ising model. We also study the multiple quantum spectra, eventually observe the buildup of quantum correlation. Further applications of this protocol could enable studies other of exotic phenomena such as many body localization, and tests of the holographic duality between quantum and gravitational systems.

quant-ph↗

arXiv2019

Pulse-width-induced polarization enhancement of optically-pumped N-V electron spin in diamond

The nitrogen-vacancy (N-V) center in diamond is a widely-used platform for quantum information processing and metrology. The electron-spin state of N-V center could be initialized and readout optically, and manipulated by resonate microwave fields. In this work, we analyze the dependence of electron-spin initialization on widths of laser pulses. We build a numerical model to simulate this process and verify the simulation results in experiment. Both simulations and experiments reveal a fact that shorter laser pulses are helpful to the electron-spin polarization. We therefore propose to use extremely-short laser pulses for electron-spin initialization. In this new scheme, the spin-state contrast could be improved about 10% in experiment by using laser pulses as short as 4 ns in width. Furthermore, we provide a mechanism to explain this effect which is due to the occupation time in the meta-stable spin-singlet states of N-V center. Our new scheme is applicable in a broad range of NV-based applications in the future.

quant-ph↗

arXiv2019

Interpretation of the observed $Λ_b(6146)^0$ and $Λ_b(6152)^0$ states as 1$D$ bottom baryons

The measured masses and strong decays of $Λ_b(6146)^0$ and $Λ_b(6152)^0$ required us to decode them as the 1$D$ excited states with $J^P=3/2^+$ and $J^P=5/2^+$, respectively. Under the suggested assignment, the masses and total decay widths of $Λ_b(6146)^0$ and $Λ_b(6152)^0$ can be explained. As a $J^P=3/2^+$ state, the $Λ_b(6146)^0$ should mainly decay into $Σ_b(5815)π$. However, this theoretical result is in contradiction to the measurement since no significant $Λ_b(6146)^0\rightarrowΣ_b(5815)^\pmπ^\mp$ signals were observed by the LHCb. The possible explanations to this difficulty are mentioned. For completeness, we present the prediction of masses and decay widths of other unseen 1$D$ bottom baryons in this work. Our results could provide some important clues for the upcoming experiments.

hep-ph↗

arXiv2019

Dynamically Polarizing Spin Register of NV Centers in Diamond using Chopped Laser Pulses

Nuclear spins nearby nitrogen-vacancy (NV) centers in diamond are excellent quantum memory for quantum computing and quantum sensing, but are difficult to be initialized due to their weak interactions with the environment. Here we propose and demonstrate a magnetic-field-independent, deterministic and highly efficient polarization scheme by introducing chopped laser pulses into the double-resonance initialization method. With this method, we demonstrate initialization of single-nuclear-spin approaching $98.1\%$ and a $^{14}N$-$^{13}C$ double-nuclear-spin system approaching $96.8\%$ at room temperature. The initialization is limited by a nuclear-spin depolarization effect due to chopped laser excitation. Our approach could be extended to NV systems with more nuclear spins and would be a useful tool in future applications such as nano-MRI and single-cell NMR.

quant-ph↗

arXiv2019

Subdivisions of vertex-disjoint cycles in bipartite graphs

Let $n\geq 6,k\geq 0$ be two integers. Let $H$ be a graph of order $n$ with $k$ components, each of which is an even cycle of length at least $6$ and $G$ be a bipartite graph with bipartition $(X,Y)$ such that $|X|=|Y|\geq n/2$. In this paper, we show that if the minimum degree of $G$ is at least $n/2-k+1$, then $G$ contains a subdivision of $H$. This generalized an older result of Wang.

math.CO↗

arXiv2019

DeepCount: Crowd Counting with WiFi via Deep Learning

Recently, the research of wireless sensing has achieved more intelligent results, and the intelligent sensing of human location and activity can be realized by means of WiFi devices. However, most of the current human environment perception work is limited to a single person's environment, because the environment in which multiple people exist is more complicated than the environment in which a single person exists. In order to solve the problem of human behavior perception in a multi-human environment, we first proposed a solution to achieve crowd counting (inferred population) using deep learning in a closed environment with WIFI signals - DeepCout, which is the first in a multi-human environment. step. Since the use of WiFi to directly count the crowd is too complicated, we use deep learning to solve this problem, use Convolutional Neural Network(CNN) to automatically extract the relationship between the number of people and the channel, and use Long Short Term Memory(LSTM) to resolve the dependencies of number of people and Channel State Information(CSI) . To overcome the massive labelled data required by deep learning method, we add an online learning mechanism to determine whether or not someone is entering/leaving the room by activity recognition model, so as to correct the deep learning model in the fine-tune stage, which, in turn, reduces the required training data and make our method evolving over time. The system of DeepCount is performed and evaluated on the commercial WiFi devices. By massive training samples, our end-to-end learning approach can achieve an average of 86.4% prediction accuracy in an environment of up to 5 people. Meanwhile, by the amendment mechanism of the activity recognition model to judge door switch to get the variance of crowd to amend deep learning predicted results, the accuracy is up to 90%.

cs.LG↗

arXiv2018

Assigning the newly reported $Σ_b(6097)$ as a $P$-wave excited state and predicting its partners

The newly observed $Σ_b(6097)$ provides us a good chance to further construct the high excited states of the bottom baryon family. In this work, we explain the $Σ_b(6097)$ to be a $1P$ state with $J^P=5/2^-$ or $3/2^-$ by giving the mass spectrum analysis and the strong decay calculation, and predict the existence of $1P$ and $2S$ partners of the $Σ_b(6097)$, where their masses and the corresponding decay behaviors are presented. Because of the success of describing the $Σ_b(6097)$ and the former observed $Ξ_b(6227)$ under the quasi-two-body treatment to the bottom baryons, we continue to predict the $Ω_b$ partners of $Σ_b(6097)$ by the same method, which are the $1P$ and $2S$ states of the $bss$ baryon system. Identifying these predicted bottom baryons will be a research topic full of challenge and opportunity for future experiments especially the LHCb.

hep-ph↗

arXiv2018

Role of newly discovered $Ξ_b(6227)^-$ for constructing excited bottom baryon family

Selecting the newly observed $Ξ_b(6227)^-$ by LHCb as a study example, we decode its inner structure by giving the mass spectrum analysis and the investigation of its two-body strong decay behaviors. Our result indicates that the $Ξ_b(6227)^-$ is a good candidate of the $P$-wave $Ξ_b^{\prime}$ state with $J^P=3/2^-$ or $5/2^-$. In addition, we further provide the information of the properties of the partners of the $Ξ_b(6227)^-$. These predicted states include three $2S$ states and the remaining $1P$ states in the bottom-strange baryon family. The calculated sizable Okubo-Zweig-Iizuka$-$allowed decay widths of these partners show that the experimental search for them becomes possible via LHCb. We have a reason to believe that the present study can be treated as a start point for constructing the highly excited bottom baryon spectroscopy.

hep-ph↗

arXiv2018

Quantum state tomography of a single electron spin in diamond with Wigner reconstruction

We present the experimental reconstruction of the Wigner function of an individual electronic spin qubit associated with a nitrogen-vacancy (NV) center in diamond at room temperature. This spherical Wigner function contains the same information as the density matrix for arbitrary spin systems. As an example, we exactly characterize the quantum state of a single qubit undergoing a nearly pure dephasing process by Wigner function. The fidelities and purities during this process are extracted from the experimental reconstructed Wigner functions, whose dynamics agree with the theoretical prediction. Our method can be applied to multi-qubit systems for measuring the Wigner function of their collective spin state.

quant-ph↗

arXiv2017

New $Ω_c^0$ baryons discovered by LHCb as the members of $1P$ and $2S$ states

Inspired by the newly observed $Ω_c^0$ states at LHCb, we decode their properties by performing an analysis of mass spectrum and decay behavior. Our studies show that the five narrow states, i.e., $Ω_c(3000)^0$, $Ω_c(3050)^0$, $Ω_c(3066)^0$, $Ω_c(3090)^0$, and $Ω_c(3119)^0$, could be grouped into the $1P$ states with negative parity. Among them, the $Ω_c(3000)^0$ and $Ω_c(3090)^0$ states could be the $J^P=1/2^-$ candidates, while $Ω_c(3050)^0$ and $Ω_c(3119)^0$ are suggested as the $J^P=3/2^-$ states. $Ω_c(3066)^0$ could be regarded as a $J^P=5/2^-$ state. Since the the spin-parity, the electromagnetic transitions, and the possible hadronic decay channels $Ω_c^{(\ast)}π$ have not been measured yet, other explanations are also probable for these narrow $Ω_c^0$ states. Additionally, we discuss the possibility of the broad structure $Ω_c(3188)^0$ as a $2S$ state with $J^P=1/2^+$ or $J^P=3/2^+$. In our scheme, $Ω_c(3119)^0$ cannot be a $2S$ candidate.

hep-ph↗

arXiv2017

Spectroscopy of singly, doubly, and triply bottom baryons

Recently, some singly bottom baryons have been established experimentally, but none of doubly or triply bottom baryons has been observed. Under the Regge phenomenology, the mass of a ground state unobserved doubly or triply bottom baryon is expressed as a function of masses of the well established light baryons and singly bottom baryons. Then, the values of Regge slopes and Regge intercepts for baryons containing one, two, or three bottom quarks are calculated. After that, masses of the orbitally excited singly, doubly, and triply bottom baryons are estimated. Our predictions may be useful for the discovery of these baryons and the $J^P$ assignment of them.

hep-ph↗

arXiv2017

Newly observed $Λ_c(2860)^+$ at LHCb and its \emph{D}-wave partners $Λ_c(2880)^+$, $Ξ_c(3055)^+$ and $Ξ_c(3080)^+$

New resonance $Λ_c(2860)^+$, reported by LHCb, is a key to establish \emph{D}-wave charmed and charmed-strange baryon families. In this work, we first carry out an analysis of mass spectra of the $λ$-mode excited charmed and charmed-strange baryon states, which may reveal the relation of $Λ_c(2860)^+$, $Λ_c(2880)^+$, $Ξ_c(3055)^+$ and $Ξ_c(3080)^+$, $i.e.$, $Λ_c(2860)^+$ and $Λ_c(2880)^+$ can form a \emph{D}-wave doublet $[3/2^+,5/2^+]$ while $Ξ_c(3055)^+$ and $Ξ_c(3080)^+$ are the strange partners of $Λ_c(2860)^+$ and $Λ_c(2880)^+$, respectively. Further study of their two-body Okubo-Zweig-Iizuka-allowed decays supports $Λ_c(2860)^+$ and $Ξ_c(3055)^+$ as the \emph{D}-wave charmed and charmed-strange baryons, respectively, with $J^P=3/2^+$. For $Λ_c(2880)^+$ and $Ξ_c(3080)^+$, however, there exist some difficulties under the \emph{D}-wave assignment with $J^P=5/2^+$ since the experimental widths and some ratios of partial width of $Λ_c(2880)^+$ and $Ξ_c(3080)^+$ cannot be reproduced in our calculation.

hep-ph↗

arXiv2017

Low-lying charmed and charmed-strange baryon states

In this work, we systematically study the mass spectra and strong decays of $1P$ and $2S$ charmed and charmed-strange baryons in the framework of nonrelativistic constituent quark models. With the light quark cluster-heavy quark picture, the masses are simply calculated by a potential model. The strong decays are studied by the Eichten-Hill-Quigg decay formula. Masses and decay properties of the well-established $1S$ and $1P$ states can be reproduced by our method. $Σ_c(2800)^{0,+,++}$ can be assigned as a $Σ_{c2}(3/2^-)$ or $Σ_{c2}(5/2^-)$ state. We prefer to interpret the signal $Σ_c(2850)^0$ as a $2S(1/2^+)$ state although at present we cannot thoroughly exclude the possibility that this is the same state as $Σ_c(2800)^0$. $Λ_c(2765)^+$ or $Σ_c(2765)^+$ could be explained as the $Λ_c^+(2S)$ state or $Σ^+_{c1}(1/2^-)$ state, respectively. We propose to measure the branching ratio of $\mathcal{B}(Σ_c(2455)π)/\mathcal{B}(Σ_c(2520)π)$ in future, which may disentangle the puzzle of this state. Our results support $Ξ_c(2980)^{0,+}$ as the first radial excited state of $Ξ_c(2470)^{0,+}$ with $J^P=1/2^+$. The assignment of $Ξ_c(2930)^0$ is analogous to $Σ_c(2800)^{0,+,++}$, \emph{i.e.}, a $Ξ^\prime_{c2}(3/2^-)$ or $Ξ^\prime_{c2}(5/2^-)$ state. In addition, we predict some typical ratios among partial decay widths, which are valuable for experimental search for these missing charmed and charmed-strange baryons.

hep-ph↗

arXiv2016

Atom-light superposition oscillation and Ramsey-like atom-light interferometer

Coherent wave splitting is crucial in interferometers. Normally, the waves after this splitting are of the same type. But recent progress in interaction between atom and light has led to the coherent conversion of photon to atomic excitation. This makes it possible to split an incoming light wave into a coherent superposition state of atom and light and paves the way for an interferometer made of different types of waves. Here we report on a Rabi-like coherent-superposition oscillation observed between atom and light and a coherent mixing of light wave with excited atomic spin wave in a Raman process. We construct a new kind of hybrid interferometer based on the atom-light coherent superposition state. Interference fringes are observed in both optical output intensity and atomic output in terms of the atomic spin wave strength when we scan either or both of the optical and atomic phases. Such a hybrid interferometer can be used to interrogate atomic states by optical detection and will find its applications in precision measurement and quantum control of atoms and light.

quant-ph↗

arXiv2015

A compact 3.5-dB squeezed light source with atomic ensembles

We reported a compact squeezed light source consisting of an diode laser near resonant on 87Rb optical D1 transition and an warm Rubidium vapor cell. The -4dB vacuum squeezing at 795 nm via nonlinear magneto-optical rotation was observed when applying the magnetic field orthogonal to the propagation direction of the light beam. This compact squeezed light source can be potentially utilized in the quantum information protocols such as quantum repeater and memory, and quantum metrology such as atomic magnetometer.

quant-ph↗

arXiv2015

Masses of doubly and triply charmed baryons

Until now, the first reported doubly charmed baryon $Ξ_{cc}^{+}(3520)$ is still a puzzle. It was discovered and confirmed by SELEX collaboration, but not confirmed by LHCb, BABAR, BELLE, FOCUS, or any other collaboration. In the present paper, by employing Regge phenomenology, we first express the mass of the ground state ($L$=0) doubly charmed baryon $Ω_{cc}^{*+}$ as a function of masses of the well established light baryons and singly charmed baryons. Inserting the recent experimental data, the mass of $Ω_{cc}^{*+}$ is given to be 3809$\pm$36 MeV, which is independent of any unobservable parameters. Then, with the quadratic mass relations, we calculate the masses of the ground state triply charmed baryon $Ω_{ccc}^{++}$ and doubly charmed baryons $Ξ_{cc}^{(*)++}$, $Ξ_{cc}^{(*)+}$, and $Ω_{cc}^{+}$ (the mass of $Ξ_{cc}^{+}$ is determined as 3520$^{+41}_{-40}$ MeV, which agrees with the mass of $Ξ_{cc}^{+}(3520)$). The isospin splitting $M_{Ξ_{cc}^{++}} - M_{Ξ_{cc}^{+}} = 0.4 \pm 0.3$ MeV. After that, masses of the orbitally excited ($L$=1,2,3) doubly and triply charmed baryons are estimated. The results are reasonable comparing with those extracted in many other approaches. We suggest more efforts to study doubly and triply charmed baryons both theoretically and experimentally, not only for the abundance of baryon spectra, but also for numerically examining whether the linear mass relations or the quadratic mass relations are realized in nature. Our predictions are useful for the discovery of unobserved doubly and triply charmed baryon states and the $J^P$ assignment of these states.

hep-ph↗