Criterion for distinguishability of arbitrary bipartite orthogonal states

In this paper we present a necessary and sufficient condition of distinguishability of bipartite quantum states. It is shown that the operators to reliably distinguish states need only rounds of projective measurements and classical comunication. We also present a necessary condition of distinguishability of bipartite quantum states which is simple and general. With this condition one can get many cases of indistinguishability. The conclusions may be useful in understanding the essence of nonlocality and calculating the distillable entanglement and the bound of distillable entanglement.Comment: 7 page

Distilling multipartite pure states from a finite number of copies of multipartite mixed states

This paper will address the question of the distillation of entanglement from a finite number of multi-partite mixed states. It is shown that if one can distill a pure entangled state from n copies of a mixed state $\sigma _{ABC...}$ there must be at least a subspace in whole Hilbert space of the all copies such that the projection of $\sigma_{ABC...}^{\otimes n}$ onto the subspace is a pure entangled state. We also show that the purification of entanglement or distillation of entanglement can be carried out by local joint projective measurements with the help of classical communication and local general positive operator valued measurements on a single particle, in principle. Finally we discuss experimental realizability of the entanglement purification.Comment: to appear in PR

Distinguishing Primordial Black Holes from Astrophysical Black Holes by Einstein Telescope and Cosmic Explorer

We investigate how the next generation gravitational-wave (GW) detectors, such as Einstein Telescope (ET) and Cosmic Explorer (CE), can be used to distinguish primordial black holes (PBHs) from astrophysical black holes (ABHs). Since a direct detection of sub-solar mass black holes can be taken as the smoking gun for PBHs, we figure out the detectable limits of the abundance of sub-solar mass PBHs in cold dark matter by the targeted search for sub-solar mass PBH binaries and binaries containing a sub-solar mass PBH and a super-solar mass PBH, respectively. On the other hand, according to the different redshift evolutions of merger rate for PBH binaries and ABH binaries, we forecast the detectable event rate distributions for the PBH binaries and ABH binaries by ET and CE respectively, which can serve as a method to distinguish super-solar mass PBHs from ABHs.Comment: 9 pages, 4 figures. Update references. Accepted for publication in JCA

Distinguishing locally of quantum states and the distillation of entanglement

This paper try to probe the relation of distinguishing locally and distillation of entanglement. The distinguishing information (DI) and the maximal distinguishing information (MDI) of a set of pure states are defined. The interpretation of distillation of entanglement in term of information is given. The relation between the maximal distinguishing information and distillable entanglement is gained. As a application of this relation the distillable entanglement of Bell-diagonal states is present.Comment: 5 page

A Computational Study of Residual KPP Front Speeds in Time-Periodic Cellular Flows in the Small Diffusion Limit

The minimal speeds ($c^*$) of the Kolmogorov-Petrovsky-Piskunov (KPP) fronts at small diffusion ($\epsilon \ll 1$) in a class of time-periodic cellular flows with chaotic streamlines is investigated in this paper. The variational principle of $c^*$ reduces the computation to that of a principal eigenvalue problem on a periodic domain of a linear advection-diffusion operator with space-time periodic coefficients and small diffusion. To solve the advection dominated time-dependent eigenvalue problem efficiently over large time, a combination of finite element and spectral methods, as well as the associated fast solvers, are utilized to accelerate computation. In contrast to the scaling $c^*=\mathcal{O}(\epsilon^{1/4})$ in steady cellular flows, a new relation $c^* = \mathcal{O}(1)$ as $\epsilon \ll 1$ is revealed in the time-periodic cellular flows due to the presence of chaotic streamlines. Residual propagation speed emerges from the Lagrangian chaos which is quantified as a sub-diffusion process.Comment: 18 pages, 12 figure

Area spectra of near extremal black holes

Motivated by Maggiore's new interpretation of quasinormal modes, starting from the first law of thermodynamics of black holes, we investigate area spectra of a near extremal Schwarzschild de sitter black hole and a higher dimensional near extremal Reissner-Nordstrom de sitter black hole. We show that the area spectra of all these black holes are equally spaced and irrelevant to the parameters of black holes.Comment: V2,9 pages, references added. The section of Kerr black holes is deleted since the same conclusion has been proposed before

Rescaled range and transition matrix analysis of DNA sequences

In this paper we treat some fractal and statistical features of the DNA sequences. First, a fractal record model of DNA sequence is proposed by mapping DNA sequences to integer sequences, followed by R/S analysis of the model and computation of the Hurst exponents. Second, we consider transition between the four kinds of bases within DNA. The transition matrix analysis of DNA sequences shows that some measures of complexity based on transition proportion matrix are of interest. We use some measures of complexity to distinguish exon and intron. Regarding the evolution, we find that for species of higher grade, the transition rate among the four kinds of bases goes further from the equilibrium.Comment: 8 pages with one figure. Communication in Theoretical Physics (2000) (to appear

Local distinguishability of quantum states and the distillation of entanglement

This paper tries to probe the relation between the local distinguishability of orthogonal quantum states and the distillation of entanglement. An new interpretation for the distillation of entanglement and the distinguishability of orthogonal quantum states in terms of information is given, respectively. By constraining our discussion on a special protocol we give a necessary and sufficient condition for the local distinguishability of the orthogonal pure states, and gain the maximal yield of the distillable entanglement. It is shown that the information entropy, the locally distinguishability of quantum states and the distillation of entanglement are closely related.Comment: 4 page, the revision of quant-ph/0202165, submitte

A class of transient acceleration models consistent with Big Bang Cosmology

Is it possible that the current cosmic accelerating expansion will turn into a decelerating one? Can this transition be realized by some viable theoretical model that is consistent with the standard Big Bang cosmology? We study a class of phenomenological models of a transient acceleration, based on a dynamical dark energy with a very general form of equation of state $p_{de}=\alpha\rho_{de}-\beta\rho_{de}^m$. It mimics the cosmological constant $\rho_{de}\rightarrow$ const for small scale factor $a$, and behaves as a barotropic gas with $\rho_{de}\rightarrow a^{-3(\alpha+1)}$ with $\alpha\ge 0$ for large $a$. The cosmic evolution of four models in the class has been examined in details, and all yields a smooth transient acceleration. Depending on the specific model, the future universe may be dominated either by the dark energy or by the matter. In two models, the dynamical dark energy can be explicitly realized by a scalar field with an analytical potential $V(\phi)$. Moreover, the statistical analysis shows that the models can be as robust as $\Lambda$CDM in confronting the observational data of SN Ia, CMB, and BAO. As improvements over the previous studies, our models overcome the over-abundance problem of dark energy during early eras, and satisfy the constraints on the dark energy from WMAP observations of CMB.Comment: 11 pages, 8 figures. To be published in RA

Cosmological Constraints on Variable Warm Dark Matter

Although $\Lambda$CDM model is very successful in many aspects, it has been seriously challenged. Recently, warm dark matter (WDM) remarkably rose as an alternative of cold dark matter (CDM). In the literature, many attempts have been made to determine the equation-of-state parameter (EoS) of WDM. However, in most of the previous works, it is usually assumed that the EoS of dark matter (DM) is constant (and usually the EoS of dark energy is also constant). Obviously, this assumption is fairly restrictive. It is more natural to assume a variable EoS for WDM (and dark energy). In the present work, we try to constrain the EoS of variable WDM with the current cosmological observations. We find that the best fits indicate WDM, while CDM is still consistent with the current observational data. However, $\Lambda$CDM is still better than WDM models from the viewpoint of goodness-of-fit. So, in order to distinguish WDM and CDM, the further observations on the small/galactic scale are required. On the other hand, in this work we also consider WDM whose EoS is constant, while the role of dark energy is played by various models. We find that the cosmological constraint on the constant EoS of WDM is fairly robust.Comment: 11 pages, 6 figures, 1 table, revtex4; v2: discussions added, Phys. Lett. B in press; v3: published versio