Practical decoy-state measurement-device-independent quantum key distribution

Measurement-device-independent quantum key distribution (MDI-QKD) is immune to all the detection attacks; thus when it is combined with the decoy-state method, the final key is unconditionally secure, even if a practical weak coherent source is used by Alice and Bob. However, until now, the analysis of decoy-state MDI-QKD with a weak coherent source is incomplete. In this paper, we derive, with only vacuum+weak decoy state, some tight formulas to estimate the lower bound of yield and the upper bound of error rate for the fraction of signals in which both Alice and Bob send a single-photon pulse to the untrusted third party Charlie. The numerical simulations show that our method with only vacuum+weak decoy state can asymptotically approach the theoretical limit of the infinite number of decoy states. Furthermore, the statistical fluctuation due to the finite length of date is also considered based on the standard statistical analysis.Comment: 5 pages, 3 figure

Unbiased Correction Relations for Galaxy Cluster properties Derived from Chandra and XMM-Newton

We use a sample of 62 clusters of galaxies to investigate the discrepancies of gas temperature and total mass within r500 between XMM-Newton and Chandra data. Comparisons of the properties show that: (1) Both the de-projected and projected temperatures determined by Chandra are higher than those of XMM-Newton and there is a good linear relation for the de-projected temperature. (2) The Chandra mass is much higher than XMM-Newton mass with a bias of 0.15. To explore the reasons for the discrepancy in mass, we recalculate the Chandra mass (expressed as M_c) by modifying its temperature with the de-projected temperature relation. The results show that M_c is more close to the XMM-Newton mass with the bias reducing to 0.02. Moreover, M_c are corrected with the r500 measured by XMM-Newton and the intrinsic scatter is significantly improved with the value reducing from 0.20 to 0.12. These mean that the temperature bias may be the main factor causing the mass bias. At last, we find that M_c is consistent with the corresponding XMM-Newton mass derived directly from our mass relation at a given Chandra mass. Thus, the de-projected temperature and mass relations can provide unbiased corrections for galaxy cluster properties derived from Chandra and XMM-Newton.Comment: accepted for publication in Ap

Exploring behaviors of partonic matter forming in early stage of pppp and nucleus-nucleus collisions at ultra-relativistic energies

The parton yield, (pseudo)rapidity distribution, and transverse momentum distribution in partonic matter assumed forming in the early stage of $pp$ and nucleus-nucleus collisions at RHIC energy ($\sqrt{s_{{NN}}}$=200 GeV) and LHC energy ($\sqrt{s_{{NN}}}$=5.5 TeV for nucleus-nucleus, 5.5 and/or 14 TeV for $pp$) are comparatively investigated with parton and hadron cascade model PACIAE. It turned out that the different parton and anti-parton spectra approach to be similar with reaction energy increasing from RHIC to LHC. We have argued that if the partonic matter forming in Au+Au collisions at RHIC energy is strongly interacting quark-gluon plasma, the one forming in Pb+Pb collisions at LHC energy might approach the real (free) quark-gluon plasma.Comment: 6 pages, 6 figure

Centrality dependence of forward-backward multiplicity correlation in Au+Au collisions at sNN\sqrt{s_{NN}}=200 GeV

We have studied the centrality dependence of charged particle forward-backward multiplicity correlation strength in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV with a parton and hadron cascade model, PACIAE, based on PYTHIA. The calculated results are compared with the STAR data. The experimentally observed correlation strength characters: (1) the approximately flat pseudorapidity dependence in central collisions and (2) the monotonous decrease with decreasing centrality are well reproduced. However the theoretical results are bigger than the STAR data for the peripheral collisions. A discussion is given for the comparison among the different models and STAR data.Comment: 5pages,4figure

A classical postselected weak amplification scheme via thermal light cross-Kerr effect

In common sense, postselected weak amplification must be related to destructive interference effect of the meter system, and a single photon exerts no effect on thermal field via cross-phasemodulation (XPM) interaction. In this Letter we present, for the first time, a thermal light cross-Kerr effect. Through analysis, we reveal two unexpected results: i) postselection and weak amplification can be explained at a classical level without destructive interference, and ii) weak amplification and weak value are not one thing. After postselection a new mixed light can be generated which is nonclassical. This scheme can be realized via electromagnetically-induced transparency.Comment: Comments are welcome. 6 pages, 11 figure

Complete deterministic multi-electron Greenberger-Horne-Zeilinger state analyzer for quantum communication

We present a scheme for the multi-electron Greenberger-Horne-Zeilinger (GHZ) state analyzer, resorting to an interface between the polarization of a probe photon and the spin of an electron in a quantum dot embedded in a microcavity. All the multi-spin GHZ states can be completely discriminated by using single-photon detectors and linear optical elements. Our scheme has some features. First, it is a complete GHZ-state analyzer for multi-electron spin systems. Second, the initial entangled states remain after being identified and they can be used for a successive task. Third, the electron qubits are static and the photons play a role of a medium for information transfer, which has a good application in quantum repeater in which the electron qubits are used to store the information and the photon qubits are used to transfer the information between others.Comment: 6 page, 3 figures, 1 tabl

A good mass proxy for galaxy clusters with XMM-Newton

We use a sample of 39 galaxy clusters at redshift z < 0.1 observed by XMM-Newton to investigate the relations between X-ray observables and total mass. Based on central cooling time and central temperature drop, the clusters in this sample are divided into two groups: 25 cool core clusters and 14 non-cool core clusters, respectively. We study the scaling relations of Lbol-M500, M500-T, M500-Mg and M500-YX, and also the influences of cool core on these relations. The results show that the M500-YX relation has a slope close to the standard self-similar value, has the smallest scatter and does not vary with the cluster sample. Moreover, the M500-YX relation is not affected by the cool core. Thus, the parameter of YX may be the best mass indicator.Comment: ApJ Accepted, 25 pages, 7 figure

Hacking on decoy-state quantum key distribution system with partial phase randomization

Quantum key distribution (QKD) provides means for unconditional secure key transmission between two distant parties. However, in practical implementations, it suffers from quantum hacking due to device imperfections. Here we propose a hybrid measurement attack, with only linear optics, homodyne detection, and single photon detection, to the widely used vacuum+weak decoy state QKD system when the phase of source is partially randomized. Our analysis shows that, in some parameter regimes, the proposed attack would result in an entanglement breaking channel but still be able to trick the legitimate users to believe they have transmitted secure keys. That is, the eavesdropper is able to steal all the key information without discovered by the users. Thus, our proposal reveals that partial phase randomization is not sufficient to guarantee the security of phase-encoding QKD systems with weak coherent states.Comment: 12 pages,4 figure

The YSZ,Planck−YSZ,XMM\rm{Y_{SZ,Planck} - Y_{SZ,XMM}} scaling relation and its difference between cool-core and non-cool-core clusters

We construct a sample of 70 clusters using data from XMM-Newton and Planck to investigate the $Y_{\rm SZ,Planck}-Y_{\rm SZ, XMM}$ scaling relation and the cool-core influences on the relation. $Y_{\rm SZ,XMM}$ is calculated by accurate de-projected temperature and electron number density profiles derived from XMM-Newton. $Y_{\rm SZ,Planck}$ is the latest Planck data restricted to our precise X-ray size $\theta_{\rm 500}$. To study the cool-core influences on$Y_{\rm SZ,Planck}-Y_{\rm SZ, XMM}$ scaling relation, we apply two criteria, limits of central cooling time and classic mass deposition rate, to distinguish cool-core clusters (CCCs) from non-cool-core clusters (NCCCs). We also use $Y_{\rm SZ,Planck}$ from other papers, which are derived from different methods, to confirm our results. The intercept and slope of the$Y_{\rm SZ,Planck}-Y_{\rm SZ, XMM}$ scaling relation are $A=-0.86 \pm 0.30$, $B=0.83 \pm 0.06$. The intrinsic scatter is $\sigma_{\rm ins}= 0.14 \pm 0.03$. The ratio of \mbox{$Y_{\rm SZ,Planck}/Y_{\rm SZ, XMM}$} is $1.03 \pm 0.05$, which is perfectly agreed with unity. Discrepancies of $Y_{\rm SZ,Planck}-Y_{\rm SZ, XMM}$ scaling relation between CCCs and NCCCs are found in observation. They are independent of cool-core classification criteria and $Y_{\rm SZ,Planck}$ calculation methods, although discrepancies are more significant under the classification criteria of classic mass deposition rate. The intrinsic scatter of CCCs (0.04) is quite small compared to that of NCCCs (0.27). The ratio of $Y_{\rm SZ,Planck}/Y_{\rm SZ, XMM}$ for CCCs is $0.89 \pm 0.05$, suggesting that CCCs' $Y_{\rm SZ,XMM}$ may overestimate SZ signal. By contrast, the ratio of $Y_{\rm SZ,Planck}/Y_{\rm SZ, XMM}$ for NCCCs is $1.14 \pm 0.12$, which indicates that NCCCs' $Y_{\rm SZ,XMM}$ may underestimate SZ signal.Comment: 16 pages, 5 figures, accepted by RA

Study on possible molecular states composed of ΛcDˉ\Lambda_c\bar D (ΛbB\Lambda_b B) and ΣcDˉ\Sigma_c\bar D (ΣbB\Sigma_b B) within the Bethe-Salpeter framework

$P_c(4312)$ observed by the LHCb collaboration is confirmed as a pentaquark and its structure, production, and decay behaviors attract great attention from theorists and experimentalists. Since its mass is very close to sum of $\Sigma_c$ and $\bar D$ masses, it is naturally tempted to be considered as a molecular state composed of $\Sigma_c$ and $\bar D$. Moreover, $P_c(4312)$ is observed in the channel with $J/\psi p$ final state, requiring that isospin conservation $P_c(4312)$ is an isospin-1/2 eigenstate. In literature, several groups used various models to estimate its spectrum. We systematically study the pentaquarks within the framework of the Bethe-Salpeter equation; thus $P_c(4312)$ is an excellent target because of the available data. We calculate the spectrum of $P_c(4312)$ in terms of the Bethe-Salpter equations and further study its decay modes. Some predictions on other possible pentaquark states that can be tested in future experiments are made.Comment: 24 pages, 3 firures, accepted by PR