3,609 research outputs found

    Quantum Energy Teleportation with Electromagnetic Field: Discrete vs. Continuous Variables

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    It is well known that usual quantum teleportation protocols cannot transport energy. Recently, new protocols called quantum energy teleportation (QET) have been proposed, which transport energy by local operations and classical communication with the ground states of many-body quantum systems. In this paper, we compare two different QET protocols for transporting energy with electromagnetic field. In the first protocol, a 1/2 spin (a qubit) is coupled with the quantum fluctuation in the vacuum state and measured in order to obtain one-bit information about the fluctuation for the teleportation. In the second protocol, a harmonic oscillator is coupled with the fluctuation and measured in order to obtain continuous-variable information about the fluctuation. In the spin protocol, the amount of teleported energy is suppressed by an exponential damping factor when the amount of input energy increases. This suppression factor becomes power damping in the case of the harmonic oscillator protocol. Therefore, it is concluded that obtaining more information about the quantum fluctuation leads to teleporting more energy. This result suggests a profound relationship between energy and quantum information.Comment: 24 pages, 4 figures, to be published in Journal of Physics A: Mathematical and Theoretica

    Filling dependence of a new type of charge ordered liquid on a triangular lattice system

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    We study the recently reported characteristic gapless charge ordered state in a spinless fermion system on a triangular lattice under strong inter-site Coulomb interactions. In this state the charges are spontaneously divided into solid and liquid component, and the former solid part aligns in a Wigner crystal manner while the latter moves among them like a pinball. We show that such charge ordered liquid is stable over a wide range of filling, 1/3<n<2/31/3<n<2/3, and examine its filling dependent nature.Comment: 3 pages 3 figure

    Dynamic Soft Elasticity in Monodomain Nematic Elastomers

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    We study the linear dynamic mechanical response of monodomain nematic liquid crystalline elastomers under shear in the geometry that allows the director rotation. The aspects of time-temperature superposition are discussed at some length and Master Curves are obtained between the glassy state and the nematic transition temperature Tni. However, the time-temperature superposition did not work through the clearing point Tni, due to change from the ``soft-elasticity'' nematic regime to the ordinary isotropic rubber response. We focus on the low-frequency region of the Master Curves and establish the power-law dependence of the modulus G' ~ omega^a. This law agrees very well with the results of static stress relaxation, where each relaxation curve obeys the analogous power law G' ~ t^{-a} in the corresponding region of long times and temperatures.Comment: Latex, [epj]{svjour} style, 9 pages 11 figures submitted to Euro. Phys. J.

    Microscopic analysis of multipole susceptibility of actinide dioxides: A scenario of multipole ordering in AmO2_2

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    By evaluating multipole susceptibility of a seven-orbital impurity Anderson model with the use of a numerical renormalization group method, we discuss possible multipole states of actinide dioxides at low temperatures. In particular, here we point out a possible scenario for multipole ordering in americium dioxide. For Am4+^{4+} ion with five 5f5f electrons, it is considered that the ground state is Γ7−\Gamma_7^{-} doublet and the first excited state is Γ8−\Gamma_8^{-} quartet, but we remark that the f5f^5 ground state is easily converted due to the competition between spin-orbit coupling and Coulomb interactions. Then, we find that the Γ8−\Gamma_8^- quartet can be the ground state of AmO2_2 even for the same crystalline electric field potential. In the case of Γ8−\Gamma_8^- quartet ground state, the numerical results suggest that high-order multipoles such as quadrupole and octupole can be relevant to AmO2_2.Comment: 8 pages, 4 figures. To appear in Phys. Rev.

    Quadrupole Susceptibility of Gd-Based Filled Skutterudite Compounds

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    It is shown that quadrupole susceptibility can be detected in Gd compounds contrary to our textbook knowledge that Gd3+^{3+} ion induces pure spin moment due to the Hund's rules in an LSLS coupling scheme. The ground-state multiplet of Gd3+^{3+} is always characterized by JJ=7/2, where JJ denotes total angular momentum, but in a jj-jj coupling scheme, one ff electron in jj=7/2 octet carries quadrupole moment, while other six electrons fully occupy jj=5/2 sextet, where jj denotes one-electron total angular momentum. For realistic values of Coulomb interaction and spin-orbit coupling, the ground-state wavefunction is found to contain significant amount of the jj-jj coupling component. From the evaluation of quadrupole susceptibility in a simple mean-field approximation, we point out a possibility to detect the softening of elastic constant in Gd-based filled skutterudites.Comment: 8 pages, 4 figure

    Quantum Energy Teleportation with a Linear Harmonic Chain

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    A protocol of quantum energy teleportation is proposed for a one-dimensional harmonic chain. A coherent-state POVM measurement is performed to coupled oscillators of the chain in the ground state accompanied by energy infusion to the system. This measurement consumes a part of ground state entanglement. Depending on the measurement result, a displacement operation is performed on a distant oscillator accompanied by energy extraction from the zero-point fluctuation of the oscillator. We find that the amount of consumed entanglement is bounded from below by a positive value that is proportional to the amount of teleported energy.Comment: 23 pages, 10 figures, analysis for non-critical case is added, accepted for publication in PR

    Multipole correlations in low-dimensional f-electron systems

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    By using a density matrix renormalization group method, we investigate the ground-state properties of a one-dimensional three-orbital Hubbard model on the basis of a j-j coupling scheme. For B40≠0B_4^0 \ne 0, where B40B_4^0 is a parameter to control cubic crystalline electric field effect, one orbital is itinerant, while other two are localized. Due to the competition between itinerant and localized natures, we obtain orbital ordering pattern which is sensitive to B40B_4^0, leading to a characteristic change of Γ3g\Gamma_{3g} quadrupole state into an incommensurate structure. At B40=0B_4^0 = 0, all the three orbitals are degenerate, but we observe a peak at q=0q = 0 in Γ3g\Gamma_{3g} quadrupole correlation, indicating a ferro-orbital state, and the peak at q=πq = \pi in Γ4u\Gamma_{4u} dipole correlation, suggesting an antiferromagnetic state. We also discuss the effect of Γ4u\Gamma_{4u} octupole on magnetic anisotropy.Comment: 4 pages, 3 figures, Proceedings of ASR-WYP-2005 (September 27-29, 2005, Tokai

    Multipole as ff-Electron Spin-Charge Density in Filled Skutterudites

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    It is shown that ff-electron multipole is naturally defined as spin-charge one-electron density operator in the second-quantized form with the use of tensor operator on the analogy of multipole expansion of electromagnetic potential from charge distribution in electromagnetism. Due to this definition of multipole, it is possible to determine multipole state from a microscopic viewpoint on the basis of the standard linear response theory for multipole susceptibility. In order to discuss multipole properties of filled skutterudites, we analyze a seven-orbital impurity Anderson model by employing a numerical renormalization group method. We show our results on possible multipole states of filled skutterudite compounds.Comment: To appear in the Proceedings of International Conference on "New Quantum Phenomena in Skutterudite and Related Systems" (September 2007, Kobe, Japan

    Effective Crystalline Electric Field Potential in a j-j Coupling Scheme

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    We propose an effective model on the basis of a jj-jj coupling scheme to describe local ff-electron states for realistic values of Coulomb interaction UU and spin-orbit coupling λ\lambda, for future development of microscopic theory of magnetism and superconductivity in fnf^n-electron systems, where nn is the number of local ff electrons. The effective model is systematically constructed by including the effect of a crystalline electric field (CEF) potential in the perturbation expansion in terms of 1/λ1/\lambda. In this paper, we collect all the terms up to the first order of 1/λ1/\lambda. Solving the effective model, we show the results of the CEF states for each case of nn=2∼\sim5 with OhO_{\rm h} symmetry in comparison with those of the Stevens Hamiltonian for the weak CEF. In particular, we carefully discuss the CEF energy levels in an intermediate coupling region with λ/U\lambda/U in the order of 0.1 corresponding to actual ff-electron materials between the LSLS and jj-jj coupling schemes. Note that the relevant energy scale of UU is the Hund's rule interaction. It is found that the CEF energy levels in the intermediate coupling region can be quantitatively reproduced by our modified jj-jj coupling scheme, when we correctly take into account the corrections in the order of 1/λ1/\lambda in addition to the CEF terms and Coulomb interactions which remain in the limit of λ\lambda=∞\infty. As an application of the modified jj-jj coupling scheme, we discuss the CEF energy levels of filled skutterudites with ThT_{\rm h} symmetry.Comment: 12 pages, 7 figures. Typeset with jpsj2.cl
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