11,998 research outputs found

    New Constraints on Anisotropic Rotation of CMB Polarization

    Full text link
    The coupling of a scalar field to electromagnetic field via the Chern-Simons term will rotate the polarization directions of the cosmic microwave background radiation. The rotation angle which relies on the distribution of the scalar field on the CMB sky is direction dependent. Such anisotropies will give rise to new distortions to the power spectra of CMB polarization and it can be used to probe the detailed physics of the scalar field. In this paper we use the updated observational data to constrain the anisotropic rotation angle in a model independent way. We find that the dominant effect of the anisotropic rotation on CMB comes from its variance and it is constrained tightly by the current data.Comment: 9 pages, 2 figures, presentations are improved to match the version to appear in JCA

    One Password: An Encryption Scheme for Hiding Users' Register Information

    Full text link
    In recent years, the attack which leverages register information (e.g. accounts and passwords) leaked from 3rd party applications to try other applications is popular and serious. We call this attack "database collision". Traditionally, people have to keep dozens of accounts and passwords for different applications to prevent this attack. In this paper, we propose a novel encryption scheme for hiding users' register information and preventing this attack. Specifically, we first hash the register information using existing safe hash function. Then the hash string is hidden, instead a coefficient vector is stored for verification. Coefficient vectors of the same register information are generated randomly for different applications. Hence, the original information is hardly cracked by dictionary based attack or database collision in practice. Using our encryption scheme, each user only needs to keep one password for dozens of applications

    qq-Deformed Chern Characters for Quantum Groups SUq(N)SU_{q}(N)

    Full text link
    In this paper, we introduce an NΓ—NN\times N matrix Ο΅abΛ‰\epsilon^{a\bar{b}} in the quantum groups SUq(N)SU_{q}(N) to transform the conjugate representation into the standard form so that we are able to compute the explicit forms of the important quantities in the bicovariant differential calculus on SUq(N)SU_{q}(N), such as the qq-deformed structure constant CIJΒ K{\bf C}_{IJ}^{~K} and the qq-deformed transposition operator Ξ›\Lambda. From the qq-gauge covariant condition we define the generalized qq-deformed Killing form and the mm-th qq-deformed Chern class PmP_{m} for the quantum groups SUq(N)SU_{q}(N). Some useful relations of the generalized qq-deformed Killing form are presented. In terms of the qq-deformed homotopy operator we are able to compute the qq-deformed Chern-Simons Q2mβˆ’1Q_{2m-1} by the condition dQ2mβˆ’1=PmdQ_{2m-1}=P_{m}, Furthermore, the qq-deformed cocycle hierarchy, the qq-deformed gauge covariant Lagrangian, and the qq-deformed Yang-Mills equation are derived

    Dark matter self-interactions from the internal dynamics of dwarf spheroidals

    Full text link
    Dwarf spheroidal galaxies provide well-known challenges to the standard cold and collisionless dark matter scenario: The too-big-to-fail problem, namely the mismatch between the observed mass enclosed within the half-light radius of dwarf spheroidals and cold dark matter N-body predictions; The hints for inner constant-density cores. While these controversies may be alleviated by baryonic physics and environmental effects, revisiting the standard lore of cold and collisionless dark matter remains an intriguing possibility. Self-interacting dark matter may be the successful proposal to such a small-scale crisis. Self-interactions correlate dark matter and baryon distributions, allowing for constant-density cores in low surface brightness galaxies. Here we report the first data-driven study of the too-big-to-fail of Milky Way dwarf spheroidals within the self-interacting dark matter paradigm. We find good description of stellar kinematics and compatibility with the concentration-mass relation from recent pure cold dark matter simulations. Within this concentration-mass relation, a subset of Milky Way dwarfs are well fitted by cross sections of 0.5-3 cm2^2/g, while others point to values greater than 10 cm2^2/g.Comment: 19 pages, 3 figures, 1 table. SharedIt at https://rdcu.be/5iT

    Efficient entanglement concentration for arbitrary less-entangled NOON state assisted with single photon

    Full text link
    We put forward two efficient entanglement concentration protocols (ECPs) for distilling the maximally entangled NOON state from arbitrary less-entangled NOON state with only an auxiliary single photon. With the help of the weak cross-Kerr nonlinearities, both the two ECPs can be used repeatedly to get a high success probability. In the first ECP, the auxiliary single photon should be shared by the two parties say Alice and Bob. In the second ECP, the auxiliary single photon is only possessed by Bob, which can greatly increase the practical success probability by avoiding the transmission loss. Moreover, Bob can operate the whole protocol alone, which makes the protocol more simple. Therefore, our two ECPs, especially the second ECP may be more useful and convenient in the current quantum information processing.Comment: 10 pages, 3 figure

    Efficient entanglement purification for polarization logic Bell state with the photonic Faraday rotation

    Full text link
    Logic-qubit entanglement is a promising resource in quantum information processing, especially in future large-scale quantum networks. In the paper, we put forward an efficient entanglement purification protocol (EPP) for nonlocal mixed logic entangled states with the bit-flip error in the logic qubits of the logic Bell state, resorting to the photon-atom interaction in low-quality (Q) cavity and atomic state measurement. Different from existing EPPs, this protocol can also purify the logic phase-flip error, and the bit-flip error and the phase-flip error in physic qubit. During the protocol, we only require to measure the atom states, and it is useful for improving the entanglement of photon systems in future large-scale quantum networks.Comment: 14 page, 6 figure

    Distilling and protecting the single-photon entangled state

    Full text link
    We propose two efficient entanglement concentration protocols (ECPs) for arbitrary less-entangled single-photon entanglement (SPE). Different from all the previous ECPs, these protocols not only can obtain the maximally SPE, but also can protect the single qubit information encoded in the polarization degree of freedom. These protocols only require one pair of less-entangled single-photon entangled state and some auxiliary single photons, which makes them economical. The first ECP is operated with the linear optical elements, which can be realized in current experiment. The second ECP adopts the cross-Kerr nonlinearities. Moreover, the second ECP can be repeated to concentrate the discard states in some conventional ECPs, so that it can get a high success probability. Based on above properties, our ECPs may be useful in current and future quantum communication.Comment: 11 pages, 4 figure

    Generalized entanglement distillation

    Full text link
    We present a way for the entanglement distillation of genuine mixed state. Different from the conventional mixed state in entanglement purification protocol, each components of the mixed state in our protocol is a less-entangled state, while it is always a maximally entangled state. With the help of the weak cross-Kerr nonlinearity, this entanglement distillation protocol does not require the sophisticated single-photon detectors. Moreover, the distilled high quality entangled state can be retained to perform the further distillation. These properties make it more convenient in practical applications.Comment: 7 pages, 4 figure

    Detection of the nonlocal atomic entanglement assisted with single photons

    Full text link
    We present an efficient way for measuring the entanglement of the atoms. Through the auxiliary single photons input-output process in cavity quantum electrodynamics (QED), the concurrence of the atomic entanglement can be obtained according to the success probability of picking up the singlet states of the atoms. This protocol has three advantages: First, we do not require the sophisticated controlled-not (CNOT) gates. Second, the distributed atoms are not required to intact with each other. Third, the atomic entanglement can be distributed nonlocally, which provides its important applications in distributed quantum computation.Comment: 5 pages, 3 figure

    Origin of fermion generations from extended noncommutative geometry

    Full text link
    We propose a way to understand the 3 fermion generations by the algebraic structures of noncommutative geometry, which is a promising framework to unify the standard model and general relativity. We make the tensor product extension and the quaternion extension on the framework. Each of the two extensions alone keeps the action invariant, and we consider them as the almost trivial structures of the geometry. We combine the two extensions, and show the corresponding physical effects, i.e., the emergence of 3 fermion generations and the mass relationships among those generations. We define the coordinate fiber space of the bundle of the manifold as the space in which the classical noncommutative geometry is expressed, then the tensor product extension explicitly shows the contribution of structures in the non-coordinate base space of the bundle to the action. The quaternion extension plays an essential role to reveal the physical effect of the structure in the non-coordinate base space.Comment: 17 latex pages, no figure. Final version for publicatio
    • …
    corecore