共查询到20条相似文献,搜索用时 15 毫秒
1.
《Physics letters. A》2006,352(3):196-201
We investigate the critical behavior of pairwise entanglement at quantum phase transitions (QPT) in several exactly solvable spin models with noise in system control parameters. We show that the exact critical behavior will change due to noise. When the noise is not too large, pairwise entanglement is robust as a signature of QPT in some spin models. 相似文献
2.
Starting with the canonical ensemble over the space of pure quantum states, we obtain an integral representation for the associated partition function. This is used to calculate the magnetisation of a system of N spin- particles. The results suggest the existence of a first order phase transition that occurs at zero temperature in the absence of spin-spin interactions. 相似文献
3.
Josep Batle Majid Alkhambashi Ahmed Farouk Mosayeb Naseri Mahmood Ghoranneviss 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(2):31
Quantum correlation measures are limited in practice to a few number of parties, since no general theory is still capable of reaching the thermodynamic limit. In the present work we study entanglement and non-locality for a cluster of spins belonging to a compound that displays a magnetocaloric effect. A quantum phase transition (QPT) is induced by an external magnetic field B, in such a way that the corresponding quantum fluctuations are reproduced at a much smaller scale than the experimental outcomes, and then described by means of the aforementioned quantum measures. 相似文献
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Orús R 《Physical review letters》2008,100(13):130502
Under successive renormalization group transformations applied to a quantum state |Psi of finite correlation length xi, there is typically a loss of entanglement after each iteration. How good it is then to replace |Psi by a product state at every step of the process? In this Letter we give a quantitative answer to this question by providing first analytical and general proofs that, for translationally invariant quantum systems in one spatial dimension, the global geometric entanglement per region of size L>xi diverges with the correlation length as (c/12)log(xi/epsilon) close to a quantum critical point with central charge c, where is a cutoff at short distances. Moreover, the situation at criticality is also discussed and an upper bound on the critical global geometric entanglement is provided in terms of a logarithmic function of L. 相似文献
6.
We analyze correlations between subsystems for an extended Hubbard model exactly solvable in one dimension, which exhibits a rich structure of quantum phase transitions (QPTs). The T = 0 phase diagram is exactly reproduced by studying singularities of single-site entanglement. It is shown how comparison of the latter quantity and quantum mutual information allows one to recognize whether two-point or shared quantum correlations are responsible for each of the occurring QPTs. The method works in principle for any number D of degrees of freedom per site. As a by-product, we are providing a benchmark for direct measures of bipartite entanglement; in particular, here we discuss the role of negativity at the transition. 相似文献
7.
Y. B. Sheng F. G. Deng B. K. Zhao T. J. Wang H. Y. Zhou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(1):235-242
We present a scheme for multipartite entanglement purification of
quantum systems in a Greenberger-Horne-Zeilinger state with quantum
nondemolition detectors (QNDs). This scheme does not require the
controlled-not gates which cannot be implemented perfectly with
linear optical elements at present, but QNDs based on cross-Kerr
nonlinearities. It works with two steps, i.e., the bit-flipping
error correction and the phase-flipping error correction. These two
steps can be iterated perfectly with parity checks and simple
single-photon measurements. This scheme does not require the parties
to possess sophisticated single photon detectors. These features
maybe make this scheme more efficient and feasible than others in
practical applications. 相似文献
8.
By using the density matrix renormalization group technique, the quantum phase transitions in the frustrated Majumdar-Ghosh model are investigated. The behaviors of the conventional order parameter and the quantum entanglement entropy are analyzed in detail. The order parameter is found to peak at J2∼0.58, but not at the Majumdar-Ghosh point (J2=0.5). Although, the quantum entanglements calculated with different subsystems display dissimilarly, the extremes of their first derivatives approach to the same critical point. By finite size scaling, this quantum critical point JC2 converges to around 0.301 in the thermodynamic limit, which is consistent with those predicted previously by some authors (Tonegawa and Harada, 1987 [6]; Kuboki and Fukuyama, 1987 [7]; Chitra et al., 1995 [9]). Across the JC2, the system undergoes a quantum phase transition from a gapless spin-fluid phase to a gapped dimerized phase. 相似文献
9.
We show that one single-mode squeezed state distributed among N parties using linear optics suffices to produce a truly N-partite entangled state for any nonzero squeezing and arbitrarily many parties. From this N-partite entangled state, via quadrature measurements of N-2 modes, bipartite entanglement between any two of the N parties can be "distilled," which enables quantum teleportation with an experimentally determinable fidelity better than could be achieved in any classical scheme. 相似文献
10.
We develop a general theory of the relation between quantum phase transitions (QPTs) characterized by nonanalyticities in the energy and bipartite entanglement. We derive a functional relation between the matrix elements of two-particle reduced density matrices and the eigenvalues of general two-body Hamiltonians of d-level systems. The ground state energy eigenvalue and its derivatives, whose nonanalyticity characterizes a QPT, are directly tied to bipartite entanglement measures. We show that first-order QPTs are signaled by density matrix elements themselves and second-order QPTs by the first derivative of density matrix elements. Our general conclusions are illustrated via several quantum spin models. 相似文献
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Using the density matrix renormalization group technique, the quantum phase transitions in a frustrated spin-1/2 ladder with ferromagnetic interchain exchanges are investigated. According to our results, the two-rung entanglement is capable of describing the quantum phase transitions. Furthermore, its first order derivative is shown to be more sensitive than order parameters for determining phase boundary. Therefore, the intermediate columnar dimerized phase region is determined definitely. 相似文献
13.
We propose a simple quantum network to detect multipartite entangled states of bosons and show how to implement this network for neutral atoms stored in an optical lattice. We investigate the special properties of cluster states, multipartite entangled states, and superpositions of distinct macroscopic quantum states that can be identified by the network. 相似文献
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Yuan Tian Hong Chen Gao Yan Jingfeng Tian Xiaojun Wen 《Optical and Quantum Electronics》2013,45(12):1297-1305
Using the correlation states of the GHZ triplet, a proxy blind signature scheme is presented. Existing classical proxy signatures cannot guarantee the security with the emergency of quantum computing technology, current quantum signature schemes could only deliver unconditional security, our quantum proxy blind signature scheme has the characteristics of proxy signature, non-counterfeit, non-disavowal and blindness by adopting quantum key preparation, quantum encryption algorithm and quantum entanglement, Our quantum proxy blind signature scheme has a foreseeable application to the E-business, E-governments, and etc. 相似文献
16.
We discuss the quantum phase transitions (QPT) in N-spin chains from the point of view of collective observables. We show that the measurement space representation is a convenient tool for the analysis of phase transitions, allowing the determination of an appropriate set of macroscopic order parameters (for a given Hamiltonian). Quantum correlations in the vicinity of the critical points are analyzed both in the ground states and low temperature thermal states. 相似文献
17.
X. S. Ma A. M. Wang X. D. Yang F. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(1):135-140
We study the dynamics of multipartite entanglement under
decoherence induced by the environment consisting of a fermionic
bath. Based on the algebraic measure of entanglement-negativity, we analyze the time evolution of entanglement of both
pure states and mixed ones, and find that entanglement evolution
depends on both bath temperature and the number of qubits of
the system. A linear space SLDF which is dynamically decoupled
from the environment is identified in the sense of linear entropy
to symbolize the environment effect. 相似文献
18.
General polynomial case of Heisenberg model for spin-1 two- and three-particle clusters is considered on matter of quantum entanglement and its evolution under quantum phase transitions induced by changes of external parameters. Influence of anisotropy parameter on the phase structure and quantum entanglement is studied. The thermal evolution of quantum entanglement is also studied. Some similarities of ground state structures and phase diagrams of quantum entanglement in different planes of external parameters are considered. 相似文献
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A new simplified formula is presented to characterize genuine tripartite entanglement of (2 2 n)-dimensional quantum pure states. The formula turns out equivalent to that given in (Quant. Inf. Comp. 7(7) 584 (2007)), hence it also shows that the genuine tripartite entanglement can be described only on the basis of the local (2 2)-dimensional reduced density matrix. In particular, the two exactly solvable models of spin system studied by Yang (Phys. Rev. A 71 030302(R) (2005)) are reconsidered by employing the formula. The results show that a discontinuity in the first derivative of the formula or in the formula itself of the ground state just corresponds to the existence of quantum phase transition, which is obviously different from the concurrence. 相似文献