Equation of motion for multiqubit entanglement in multiple independent noisy channels

We investigate the possibility and conditions to factorize the entanglement evolution of a multiqubit system passing through multi-sided noisy channels. By means of a lower bound of concurrence (LBC) as entanglement measure, we derive an explicit formula of LBC evolution of the N-qubit generalized Greenberger-Horne-Zeilinger (GGHZ) state under some typical noisy channels, based on which two kinds of factorizing conditions for the LBC evolution are presented. In this case, the time-dependent LBC can be determined by a product of initial LBC of the system and the LBC evolution of a maximally entangled GGHZ state under the same multi-sided noisy channels. We analyze the realistic situations where these two kinds of factorizing conditions can be satisfied. In addition, we also discuss the dependence of entanglement robustness on the number of the qubits and that of the noisy channels.Comment: 14 page

Hilbert fractal acoustic metamaterials with negative mass density and bulk modulus on subwavelength scale

© 2019 The Authors Acoustic metamaterials (AMs) are artificially engineered composite materials, structured to have unconventional effective properties for flexibly manipulating the wave propagation, which can produce a broad range of applications such as sound cloaking and tunneling. In nature, bio-inspired fractal organization with multiple length scales has been found in various biological materials, which display enhanced dynamic properties. By introducing Hilbert curve channels, this work will design a class of topological architectures of Hilbert fractal acoustic metamaterials (HFAMs) with negative mass density and bulk modulus on subwavelength scale. In this paper, we will highlight the influences of the self-similar fractal configurations on multipole modes of HFAM. To further demonstrate multipole resonances, the pressure magnifications are assessed in the center region of HFAM with losses. Moreover, based on effective medium theory, we systematically calculate and investigate effective bulk modulus and mass density, as well as density-near-zero of HFAM, to demonstrate the negative properties and the zero-phase-difference effects of HFAMs. Numerical results show that HFAM can enable a number of applications, from sound blocking, quarter bending, sound cloaking to sound tunneling, and may further provide a possibility for the engineering guidances of the exotic properties on subwavelength scale

Atomic entanglement sudden death in a strongly driven cavity QED system

We study the entanglement dynamics of strongly driven atoms off-resonantly coupled with cavity fields. We consider conditions characterized not only by the atom-field coupling but also by the atom-field detuning. By studying two different models within the framework of cavity QED, we show that the so-called atomic entanglement sudden death (ESD) always occurs if the atom-field coupling lager than the atom-field detuning, and is independent of the type of initial atomic state