5,609 research outputs found

    Tighter weighted polygamy inequalities of multipartite entanglement in arbitrary-dimensional quantum systems

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    We investigate polygamy relations of multipartite entanglement in arbitrary-dimensional quantum systems. By improving an inequality and using the β\betath (0β10\leq\beta\leq1) power of entanglement of assistance, we provide a new class of weighted polygamy inequalities of multipartite entanglement in arbitrary-dimensional quantum systems. We show that these new polygamy relations are tighter than the ones given in [Phys. Rev. A 97, 042332 (2018)]

    Ordering states with various coherence measures

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    Quantum coherence is one of the most significant theories in quantum physics. Ordering states with various coherence measures is an intriguing task in quantification theory of coherence. In this paper, we study this problem by use of four important coherence measures -- the l1l_1 norm of coherence, the relative entropy of coherence, the geometric measure of coherence and the modified trace distance measure of coherence. We show that each pair of these measures give a different ordering of qudit states when d3d\geq 3. However, for single-qubit states, the l1l_1 norm of coherence and the geometric coherence provide the same ordering. We also show that the relative entropy of coherence and the geometric coherence give a different ordering for single-qubit states. Then we partially answer the open question proposed in [Quantum Inf. Process. 15, 4189 (2016)] whether all the coherence measures give a different ordering of states.Comment: 12 page

    Amending coherence-breaking channels via unitary operations

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    The coherence-breaking channels play a significant role in quantum information theory. We study the coherence-breaking channels and give a method to amend the coherence-breaking channels by applying unitary operations. For given incoherent channel Φ\Phi, we give necessary and sufficient conditions for the channel to be a coherence-breaking channel and amend it via unitary operations. For qubit incoherent channels Φ\Phi that are not coherence-breaking ones, we consider the mapping ΦΦ\Phi\circ\Phi and present the conditions for coherence-breaking and channel amendment as well.Comment: 8 page

    Communication-efficient three-party protocols for authentication and key agreement

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    AbstractEncrypted key exchange (EKE) authentication approaches are very important for secure communicating over public networks. In order to solve the security weaknesses three-party EKE, Yeh et al. [H.T. Yeh, H.M. Sun, T. Hwang, Efficient three-party authentication and key agreement protocols resistant to password guessing attacks, Information Science and Engineering 19 (6) (2003) 1059–1070.] proposed two secure and efficient three-party EKE protocols. Based on the protocol developed by Yeh et al., two improved EKE protocols for authentication and key agreement are proposed in this study. The computational costs of the proposed protocols are the same as those of the protocols of Yeh et al. However, the numbers of messages in the communication are fewer than those of the protocols of Yeh et al. Furthermore, the round efficient versions of our proposed protocols are also described

    Dynamics of coherence-induced state ordering under Markovian channels

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    We study the dynamics of coherence-induced state ordering under incoherent channels, particularly four specific Markovian channels: - amplitude damping channel, phase damping channel, depolarizing channel and bit flit channel for single-qubit states. We show that the amplitude damping channel, phase damping channel, and depolarizing channel do not change the coherence-induced state ordering by l1l_1 norm of coherence, relative entropy of coherence, geometric measure of coherence, and Tsallis relative α\alpha-entropies, while the bit flit channel does change for some special cases.Comment: 7 pages, 21 figure

    Novel joint-drift-free scheme at acceleration level for robotic redundancy resolution with tracking error theoretically eliminated

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    In this article, three acceleration-level joint-drift-free (ALJDF) schemes for kinematic control of redundant manipulators are proposed and analyzed from perspectives of dynamics and kinematics with the corresponding tracking error analyses. First, the existing ALJDF schemes for kinematic control of redundant manipulators are systematized into a generalized acceleration-level joint-drift-free scheme with a paradox pointing out the theoretical existence of the velocity error related to joint drift. Second, to remedy the deficiency of the existing solutions, a novel acceleration-level joint-drift-free (NALJDF) scheme is proposed to decouple Cartesian space error from joint space with the tracking error theoretically eliminated. Third, in consideration of the uncertainty at the dynamics level, a multi-index optimization acceleration-level joint-drift-free scheme is presented to reveal the influence of dynamics factors on the redundant manipulator control. Afterwards, theoretical analyses are provided to prove the stability and feasibility of the corresponding dynamic neural network with the tracking error deduced. Then, computer simulations, performance comparisons, and physical experiments on different redundant manipulators synthesized by the proposed schemes are conducted to demonstrate the high performance and superiority of the NALJDF scheme and the influence of dynamics parameters on robot control. This work is of great significance to enhance the product quality and production efficiency in industrial production

    High sensitivity HI image of diffuse gas and new tidal features in M51 observed by FAST

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    We observed the classical interacting galaxy M51 with FAST and obtain high sensitivity HI image with column density down to 3.8 ×\times 1018^{18} cm2^{-2}. In the image we can see a diffuse extended envelope around the system and several new tidal features. We also get a deeper look at M51b's probable gas, which has an approximated velocity range of 560 to 740 km s1^{-1} and a flux of 7.5 Jy km s1^{-1}. Compared to the VLA image, we observe more complete structures of the Southeast Tail, Northeast Cloud and Northwest Plume, as well as new features of the Northwest Cloud and Southwest Plume. M51's most prominent tidal feature, the Southeast Tail, looks very long and broad, in addition with two small detached clouds at the periphery. Due to the presence of optical and simulated counterparts, the Northwest cloud appears to be the tail of M51a, while the Northwest Plume is more likely a tidal tail of M51b. The large mass of the Northwest Plume suggests that M51b may have been as gas-rich as M51a before the interaction. In addition, the formation process of the Northeast Cloud and Southwest Plume is obscured by the lack of optical and simulated counterparts. These novel tidal features, together with M51b's probable gas, will inspire future simulations and provide a deeper understanding of the evolution of this interacting system.Comment: 11 pages, 9 figures, accepted for publication in MNRA

    Quantum Fisher information-based detection of genuine tripartite entanglement

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    Genuine multipartite entanglement plays important roles in quantum information processing. The detection of genuine multipartite entanglement has been long time a challenging problem in the theory of quantum entanglement. We propose a criterion for detecting genuine tripartite entanglement of arbitrary dimensional tripartite states based on quantum Fisher information. We show that this criterion is more effective for some states in detecting genuine tripartite entanglement by detailed example.Comment: 12 pages, 2 figure
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