arXiv subjects

Ying Li

Publications and source records attributed to Ying Li.

At least 559 records · Page 31Linked to original sources

arXiv2015

Pure Annihilation Type $B \to K_0^{\pm}(1430)K^{()\mp}$ Decays in the Family Non-universal $Z^\prime$ Model

By assuming that the scalar meson $K_0^*(1430)$ belongs to the first excited states or the lowest lying ground states, we study the pure annihilation-type decays $B \to K_0^{*\pm}(1430)K^{(*)\mp}$ in the QCD factorization approach. Within the standard model, the branching fractions are at the order of $10^{-8}-10^{-7}$, which is possible to be measured in the ongoing LHCb experiment or forthcoming Belle-II experiment. We also study these decays in the family non-universal $Z^\prime$ model. The results show that if $m_{Z^\prime}\approx 600\mathrm{GeV}$ ($ζ=0.02$), both the branching fractions and $CP$ asymmetries of $\overline B^0\to K_0^{*+}(1430)K^-$ could be changed remarkably, which provides us a place for probing the effect of new physics. These results could be used to constrain the parameters of $Z^\prime$ model.

hep-ph↗

arXiv2015

Resource costs for fault-tolerant linear optical quantum computing

Linear optical quantum computing (LOQC) seems attractively simple: information is borne entirely by light and processed by components such as beam splitters, phase shifters and detectors. However this very simplicity leads to limitations, such as the lack of deterministic entangling operations, which are compensated for by using substantial hardware overheads. Here we quantify the resource costs for full scale LOQC by proposing a specific protocol based on the surface code. With the caveat that our protocol can be further optimised, we report that the required number of physical components is at least five orders of magnitude greater than in comparable matter-based systems. Moreover the resource requirements grow higher if the per-component photon loss rate is worse than one in a thousand, or the per-component noise rate is worse than $10^{-5}$. We identify the performance of switches in the network as the single most influential factor influencing resource scaling.

quant-ph↗

arXiv2015

Impact of Family Non-universal $Z^\prime$ Boson on Pure Annihilation $B_s \to π^+ π^-$ and $B_d \to K^+ K^-$ Decays

We study the $B_s \to π^+ π^-$ and $B_d \to K^+ K^-$ decays in the standard model and the family non-universal $Z^\prime$ model. Since none of the quarks in final states is the same as the initial quark, these decay modes can occur only via power-suppressed annihilation diagrams. Despite the consistence of the standard model prediction with the available data, there is a surviving room for a light $Z^\prime$ boson. Taking into account the $Z^\prime$ contribution, we find theoretical results for branching fractions can better accommodate the data. With the relevant data, we also derive a constraint on the parameter space for the $Z^\prime$. Moreover, for the $B_d \to K^+ K^-$, both the direct and the mixing-induced $CP$ asymmetry are sensitive to the couplings between $Z^\prime$ and fermions in the parameter spaces constrained by data. The measurements at future experimental facilities, including the LHC-b, Belle-II and the proposed high energy $e^+e^-$ collider, will provide us useful hints for direct searching for the light $Z^\prime$ boson.

hep-ph↗

arXiv2015

Study of $B \to K_0^(1430)K^{()}$ decays in QCD Factorization Approach

Within the QCD factorization approach, we calculate the branching fractions and $CP$ asymmetry parameters of 12 $B \to K_0^*(1430)K^{(*)}$ decay modes under the assumption that the scalar meson $K_0^*(1430)$ is the first excited state or the lowest lying ground state in the quark model. We find that the decay modes with the scalar meson emitted, have large branching fractions due to the enhancement of large chiral factor $r_χ^{K_0^*}$. The branching fractions of decays with the vector meson emitted, become much smaller owing to the smaller factor $r_χ^{K^*}$. Moreover, the annihilation type diagram will induce large uncertainties because of the extra free parameter dealing with the endpoint singularity. For the pure annihilation type decays, our predictions are smaller than that from PQCD approach by 2-3 orders of magnitudes. These results will be tested by the ongoing LHCb experiment, forthcoming Belle-II experiment and the proposing circular electron-positron collider.

hep-ph↗

arXiv2015

Improved Estimates of The $B_{(s)}\to V V$ Decays in Perturbative QCD Approach

We reexamine the branching ratios, $CP$-asymmetries, and other observables in a large number of $B_q\to VV(q=u,d,s)$ decays in the perturbative QCD (PQCD) approach, where $V$ denotes a light vector meson $(ρ, K^*, ω, ϕ)$. The essential difference between this work and the earlier similar works is of parametric origin and in the estimates of the power corrections related to the ratio $r_i^2=m_{V_i}^2/m_B^2(i=2,3)$ ($m_V$ and $m_B$ denote the masses of the vector and $B$ meson, respectively). In particular, we use up-to-date distribution amplitudes for the final state mesons and keep the terms proportional to the ratio $r_i^2$ in our calculations. Our updated calculations are in agreement with the experimental data, except for a limited number of decays which we discuss. We emphasize that the penguin annihilation and the hard-scattering emission contributions are essential to understand the polarization anomaly, such as in the $B\to ϕK^*$ and $B_s \to ϕϕ$ decay modes. We also compare our results with those obtained in the QCD factorization (QCDF) approach and comment on the similarities and differences, which can be used to discriminate between these approaches in future experiments.

hep-ph↗

arXiv2014

Measurement-Based Quantum Computation on Two-Body Interacting Qubits with Adiabatic Evolution

A cluster state cannot be a unique ground state of a two-body interacting Hamiltonian. Here, we propose the creation of a cluster state of logical qubits encoded in spin-1/2 particles by adiabatically weakening two-body interactions. The proposal is valid for any spatial dimensional cluster states. Errors induced by thermal fluctuations and adiabatic evolution within finite time can be eliminated ensuring fault-tolerant quantum computing schemes.

quant-ph↗

arXiv2014

A magic state's fidelity can be superior to the operations that created it

The leading approach to fault tolerant quantum computing requires a continual supply of magic states. When a new magic state is first encoded, its initial fidelity will be too poor for use in the computation. This necessitates a resource-intensive distillation process that occupies the majority of the computer's hardware; creating magic states with a high initial fidelity minimises this cost and is therefore crucial for practical quantum computing. Here we present the surprising and encouraging result that raw magic states can have a fidelity significantly better than that of the two-qubit gate operations used to construct them. Our protocol exploits post-selection without significantly slowing the rate of generation and tolerates finite error rates in initialisations, measurements and single-qubit gates. This approach may dramatically reduce the size of the hardware needed for a given quantum computing task.

quant-ph↗

arXiv2014

Analysis of the optical conductivity for A2IrO3 (A = Na, Li) from first principles

We present results for the optical conductivity of Na2IrO3 within density functional theory by including spin-orbit (SO) and correlation effects (U) as implemented in GGA+SO+U. We identify the various interband transitions and show that the underlying quasi-molecular-orbital nature of the electronic structure in Na2IrO3 translates into distinct features in the optical conductivity. Most importantly, the parity of the quasi-molecular orbitals appears to be the main factor in determining strong and weak optical transitions. We also present optical conductivity calculations for Li2IrO3 and discuss the similarities and differences with Na2IrO3.

cond-mat.str-el↗

arXiv2014

BRVST: Efficient and Content-Expressive Information Matching Overlay in Wireless Networks

Efficient and flexible information matching over wireless networks has become increasingly important and challenging with the popularity of smart devices and the growth of social-network-based applications. Some existing approaches designed for wired networks are not applicable to wireless networks, due to their overwhelming control overheads. In this paper, we propose a reliable and scalable binary range vector summary tree (BRVST) infrastructure for flexible information expression support, effective content matching and timely information dissemination over the dynamic wireless network. A novel attribute range vector structure has been introduced for efficient and accurate content representation and a summary tree structure to facilitate information aggregation. For robust and scalable operations over dynamic wireless network, the proposed overlay system exploits a virtual hierarchical geographic management framework. Extensive simulations demonstrate that BRVST has a significantly faster event matching speed, while incurs very low storage and traffic overhead, as compared with peer schemes tested.

cs.NI↗

arXiv2014

Branching Fractions and Direct CP Asymmetries of $\bar B_s ^0 \to K^0 h^+h^{\prime -}(h^{(\prime)}=K,π)$ Decays

Motivated by the recent LHCb collaboration measurements of charmless three-body decays of $\bar B_s^0$ meson, we calculate the branching fractions of $\bar B_s ^0 \to K^0 π^+π^-$, $\bar B_s ^0 \to K^0 K^+K^-$, $\bar B_s ^0 \to K^0 π^+K^-$ and $\bar B_s ^0 \to \bar K^0 K^+π^-$ decay modes using the factorization approach. Both the resonant and nonresonant contributions are studied in detail. For the decays $\bar B_s ^0 \to K^0 π^+π^-$ and $\bar B_s ^0 \to K^0 K^+K^-$, our results agree well with experimental data, and the former is dominated by the $K^*$, while the latter one is dominated by the nonresonant contribution. Considering the flavor SU(3) symmetry violation, the sum of branching fractions of $\bar B_s ^0 \to K^0 π^+K^-$ and $\bar B_s ^0 \to \bar K^0 K^+π^-$ could accommodate the data well too. It should be noted that both branching fractions are sensitive to the scalar density $< Kπ| \bar s q|0>$. Furthermore, the resonant contributions are dominated by the scalar $K_0^*(1430)$. We hope that these branching fractions could be measured individually in the experiments so as to test the factorization approach and the flavor SU(3) asymmetry. Moreover, the direct CP asymmetries of these decays are also investigated, which could be measured in the running LHCb experiment and Super-b factory in the future.

hep-ph↗

arXiv2014

Training-Free Non-Intrusive Load Monitoring of Electric Vehicle Charging with Low Sampling Rate

Non-intrusive load monitoring (NILM) is an important topic in smart-grid and smart-home. Many energy disaggregation algorithms have been proposed to detect various individual appliances from one aggregated signal observation. However, few works studied the energy disaggregation of plug-in electric vehicle (EV) charging in the residential environment since EVs charging at home has emerged only recently. Recent studies showed that EV charging has a large impact on smart-grid especially in summer. Therefore, EV charging monitoring has become a more important and urgent missing piece in energy disaggregation. In this paper, we present a novel method to disaggregate EV charging signals from aggregated real power signals. The proposed method can effectively mitigate interference coming from air-conditioner (AC), enabling accurate EV charging detection and energy estimation under the presence of AC power signals. Besides, the proposed algorithm requires no training, demands a light computational load, delivers high estimation accuracy, and works well for data recorded at the low sampling rate 1/60 Hz. When the algorithm is tested on real-world data recorded from 11 houses over about a whole year (total 125 months worth of data), the averaged error in estimating energy consumption of EV charging is 15.7 kwh/month (while the true averaged energy consumption of EV charging is 208.5 kwh/month), and the averaged normalized mean square error in disaggregating EV charging load signals is 0.19.

cs.OH↗

arXiv2014

Electrically driven spin resonance in a bent disordered carbon nanotube

Resonant manipulation of carbon nanotube valley-spin qubits by an electric field is investigated theoretically. We develop a new analysis of electrically driven spin resonance exploiting fixed physical characteristics of the nanotube: a bend and inhomogeneous disorder. The spectrum is simulated for an electron valley-spin qubit coupled to a hole valley-spin qubit and an impurity electron spin, and features that coincide with a recent measurement are identified. We show that the same mechanism allows resonant control of the full four-dimensional spin-valley space.

cond-mat.mes-hall↗

arXiv2014

Generation of cylindrical vector vortex beams by two cascaded metasurfaces

We present a simple and efficient method to generate any cylindrical vector vortex (CVV) beams based on two cascaded metasurfaces. The metasurface works as a space-variant Panchratnam-Berry phase element and can produce any desirable vortex phase and vector polarization. The first metasurface is used to switch the sign of topological charges associated with vortex, and the second metasurface is applied to manipulate the local polarization. This method allows us to simultaneously manipulate polarization and phase of the CVV beams.

physics.optics↗

arXiv2014

Spectral observations of Ellerman bombs and fitting with a two-cloud model

We study the H$α$ and Ca II 8542 Å line spectra of four typical Ellerman bombs (EBs) in active region NOAA 11765 on 2013 June 6, observed with the Fast Imaging Solar Spectrograph installed at the 1.6 meter New Solar Telescope at Big Bear Solar Observatory. Considering that EBs may occur in a restricted region in the lower atmosphere, and that their spectral lines show particular features, we propose a two-cloud model to fit the observed line profiles. The lower cloud can account for the wing emission, and the upper cloud is mainly responsible for the absorption at line center. After choosing carefully the free parameters, we get satisfactory fitting results. As expected, the lower cloud shows an increase of the source function, corresponding to a temperature increase of 400--1000 K in EBs relative to the quiet Sun. This is consistent with previous results deduced from semi-empirical models and confirms that a local heating occurs in the lower atmosphere during the appearance of EBs. We also find that the optical depths can increase to some extent in both the lower and upper clouds, which may result from either a direct heating in the lower cloud, or illumination by an enhanced radiation on the upper cloud. The velocities derived from this method, however, are different from those obtained using the traditional bisector method, implying that one should be cautious when interpreting this parameter. The two-cloud model can thus be used as an efficient method to deduce the basic physical parameters of EBs.

astro-ph.SR↗

arXiv2014

Classical noise assists the flow of quantum energy by `momentum rejuvenation'

An important challenge in quantum science is to fully understand the efficiency of energy flow in networks. Here we present a simple and intuitive explanation for the intriguing observation that optimally efficient networks are not purely quantum, but are assisted by some interaction with a `noisy' classical environment. By considering the system's dynamics in both the site-basis and the momentum-basis, we show that the effect of classical noise is to sustain a broad momentum distribution, countering the depletion of high mobility terms which occurs as energy exits from the network. This picture predicts that the optimal level of classical noise is reciprocally related to the linear dimension of the lattice; our numerical simulations verify this prediction to high accuracy for regular 1D and 2D networks over a range of sizes up to thousands of sites. This insight leads to the discovery that dramatic further improvements in performance occur when a driving field targets noise at the low mobility components.

quant-ph↗

arXiv2014

Full Investigation on the Dynamics of Power-Law Kinetic Quintessence

We give a full investigation on the dynamics of power-law kinetic quintessence $L(X, ϕ)=V(ϕ)(-X+X^2)$ by considering the potential related parameter $Γ$($=\frac{V V''}{V'^2}$) as a function of another potential parameter $λ$($=\frac{V'}{κV^{3/2}}$), which correspondingly extends the analysis of the dynamical system of our universe from two-dimension to three-dimension. Beside the critical points found in previous papers, we find a new de-Sitter-like dominant attractor(\textit{cp$6$}) and give its stable condition using the center manifold theorem. For the dark energy dominant solution(\textit{cp$6$} and \textit{cp$7$}), it could be distinguished from canonical quintessence and tachyon models since the sound speed $c_s^2=0$ or $c_s^2\ll 1$. For the scaling solution (\textit{cp$8$}), it is very interesting that the sound speed $c_s^2=1/5$ while it behaves as ordinary matter. We therefore point out that the power-law kinetic quintessence should have different signatures on cold dark matter power spectrum and cosmic microwave background both at early time when this scalar field is an early dark energy with $Ω_ϕ$ being non-negligible at high redshift and at late time when it drives the accelerating expansion. We even do not know whether there are any degeneracies of the impacts between these two epoches. They are expected to be investigated in future.

gr-qc↗

arXiv2014

Transitions in the quantum computational power

We construct two spin models on lattices (both two and three-dimensional) to study the capability of quantum computational power as a function of temperature and the system parameter. There exists a finite region in the phase diagram such that the thermal equilibrium states are capable of providing a universal fault-tolerant resource for measurement-based quantum computation. Moreover, in such a region the thermal resource states on the 3D lattices can enable topological protection for quantum computation. The two models behave similarly in terms of quantum computational power. However, they have different properties in terms of the usual phase transitions. The first model has a first-order phase transition only at zero temperature whereas there is no transition at all in the second model. Interestingly, the transition in the quantum computational power does not coincide with the phase transition in the first model.

quant-ph↗

arXiv2014

Comprehensive Study of $\overline B^0\to K^0(\overline K^0) K^\mpπ^\pm$ Decays in the Factorization Approach

Using the factorization approach, we investigate the $\overline B^0 \to \overline K^0K^+π^-$ and $\overline B^0 \to K^0K^-π^+$ decays individually including the resonant and nonresonant contributions. Under the flavor SU(3) symmetry, we obtain the total branching fraction $BR [\overline B^0 \to (\overline K^0K^+π^-+K^0K^-π^+)]=(7.17^{+0.50+1.97+0.08}_{-0.53-1.42-0.07})\times 10^{-6}$, which is in agreement with the recent measurements of BaBar and LHCb within errors. For the decay $\overline B^0 \to \overline K^0K^+π^-$, the nonresonant background and $a_0^+(1450)$ pole in the current-induced process provide large contribution, the latter of which has not been included in previous studies. On the contrary,the decay $\overline B^0 \to K^0K^-π^+$ is dominated by the nonresonant background and the offshell $ρ^-$ pole. When the flavor SU(3) symmetry breaking and the final-state rescattering are considered under two different scenarios, the results can also accommodate the experimental data with large uncertainties. Moreover, the direct $CP$ asymmetry of $\overline B^0 \to \overline K^0K^+π^-$ is found to be sensitive to the matrix element of scalar density. These predictions could be further tested in the LHCb experiment or Super-b factory in future.

hep-ph↗