Protecting entanglement from correlated amplitude damping channel using weak measurement and quantum measurement reversal

Based on the quantum technique of weak measurement, we propose a scheme to protect the entanglement from correlated amplitude damping decoherence. In contrast to the results of memoryless amplitude damping channel, we show that the memory effects play a significant role in the suppression of entanglement sudden death and protection of entanglement under severe decoherence. Moreover, we find that the initial entanglement could be drastically amplified by the combination of weak measurement and quantum measurement reversal even under the correlated amplitude damping channel. The underlying mechanism can be attributed to the probabilistic nature of weak measurements.Comment: 11 pages, 5 figures, accepted by Quantum Information Processin

Enhanced quantum teleportation in the background of Schwarzschild spacetime by weak measurements

It is commonly believed that the fidelity of quantum teleportation in the gravitational field would be degraded due to the heat up by the Hawking radiation. In this paper, we point out that the Hawking effect could be eliminated by the combined action of pre- and post-weak measurements, and thus the teleportation fidelity is almost completely protected. It is intriguing to notice that the enhancement of fidelity could not be attributed to the improvement of entanglement, but rather to the probabilistic nature of weak measurements. Our work extends the ability of weak measurements as a quantum technique to battle against gravitational decoherence in relativistic quantum information.Comment: 9 pages, 5 figures, comments are welcom

Robust Spin Squeezing Preservation in Photonic Crystal Cavities

We show that the robust spin squeezing preservation can be achieved by utilizing detuning modification for an ensemble of N separate two-level atoms embedded in photonic crystal cavities (PCC). In particular, we explore the different dynamical behaviors of spin squeezing between isotropic and anisotropic PCC cases when the atomic frequency is inside the band gap. In both cases, it is shown that the robust preservation of spin squeezing is completely determined by the formation of bound states. Intriguingly, we find that unlike the isotropic case where steady-state spin squeezing varies smoothly when the atomic frequency moves from the inside to the outside band edge, a sudden transition occurs for the anisotropic case. The present results may be of direct importance for, e.g., quantum metrology in open quantum systems.Comment: 6 pages, 4 figures, accepted by Laser Physics Letter

Enhancing teleportation of quantum Fisher information by partial measurements

The purport of quantum teleportation is to completely transfer information from one party to another distant partner. However, from the perspective of parameter estimation, it is the information carried by a particular parameter, not the information of total quantum state that needs to be teleported. Due to the inevitable noise in environment, we propose two schemes to enhance quantum Fisher information (QFI) teleportation under amplitude damping noise with the technique of partial measurements. We find that post partial measurement can greatly enhance the teleported QFI, while the combination of prior partial measurement and post partial measurement reversal could completely eliminate the effect of decoherence. We show that, somewhat consequentially, enhancing QFI teleportation is more economic than that of improving fidelity teleportation. Our work extends the ability of partial measurements as a quantum technique to battle decoherence in quantum information processing.Comment: Revised version, minor changes, accepted by Phys. Rev.

Positive-partial-transpose distinguishability for lattice-type maximally entangled states

We study the distinguishability of a particular type of maximally entangled states -- the "lattice states" using a new approach of semidefinite program. With this, we successfully construct all sets of four ququad-ququad orthogonal maximally entangled states that are locally indistinguishable and find some curious sets of six states having interesting property of distinguishability. Also, some of the problems arose from \cite{CosentinoR14} about the PPT-distinguishability of "lattice" maximally entangled states can be answered.Comment: It's rewritten. We deleted the original section II about PPT-distinguishability of three ququad-ququad MESs. Moreover, we have joined new section V which discuss PPT-distinguishability of lattice MESs for cases $t=3$ and $t=4$ . As a result, the sequence of the theorems in our article has been changed. And we revised the title of our articl

Asymmetric Supercapacitors With Dominant Pseudocapacitance Based on Manganese Oxide Nanoflowers in a Neutral Aqueous Electrolyte

Unique MnO2 nanoflowers (∼25 nm) composed of ultrathin K0.26MnO2 nanoflake assemblies were synthesized by a facile and green procedure. Prototype MnO2-NFs//KCl//CNTs asymmetric supercapacitors in a neutral aqueous electrolyte demonstrated pseudocapacitive dominance for the first time in addition to outstanding energy and power densities and superior cycling performance

Distinguishability-based genuine nonlocality with genuine multipartite entanglement

A set of orthogonal multipartite quantum states is said to be distinguishability-based genuinely nonlocal (also genuinely nonlocal, for abbreviation) if the states are locally indistinguishable across any bipartition of the subsystems. This form of multipartite nonlocality, although more naturally arising than the recently popular "strong nonlocality" in the context of local distinguishability, receives much less attention. In this work, we study the distinguishability-based genuine nonlocality of a special type of genuinely multipartite entangled states -- the Greenberger-Horne-Zeilinger (GHZ)-like states. We first show that any 5 states of the three-qubit GHZ basis are genuinely nonlocal, while any 4 states of them are not. Then for more general tripartite systems, we present a universal bound about the cardinality for an arbitrary set of GHZ-like states to be genuinely nonlocal. Although not necessary, entanglement is believed to raise difficulty in state discrimination in many situations. In the literature, there has been lots of studies in favor of this perspective, including the efforts seeking for small nonlocal sets consisting of maximally entangled states in bipartite systems. Here in the tripartite case, where GHZ-like states are studied, we also find the existence of some small genuinely nonlocal sets: we show that the cardinality can scale down to linear in the local dimension d. This result not only substantiates the aforemention perspective in multipartite scenario, but also suggests that there might exist substantial difference between strong nonlocality and the normal distinguishability-based multipartite nonlocality.Comment: 13 pages, 1 figure, submitted to "New journal of physics" in Sep, 202

TiO 2 Fibers: Tunable Polymorphic Phase Transformation and Electrochemical Properties

A series of one-dimensional (1D) nanoparticle-assembled TiO2 fibers with tunable polymorphs were prepared via a novel and large scale ForceSpinning® process of titanium tetraisopropoxide (TTIP)/polyvinylpyrrolidone (PVP) precursor fibers followed with a thermal treatment at various calcinations temperatures. The thermal and structural transformations were characterized by thermogravimetric analysis/differential scanning calorimetry, scanning electron microscopy, and X-ray diffraction. The influence of polymorphic phase of the TiO2 fibers on the electrochemical performance in neutral aqueous 1 M Na2SO4 electrolyte was investigated. The polymorphic amorphous/anatase/rutile TiO2 fibers prepared at 450 °C achieved a highest capacitance of 21.2 F g−1 (6.61 mF cm−2) at a current density of 200 mA g−1, for which the improved electronic conductivity and activated pseudo-capacitance mechanism may be responsible. This work helps bridge the gap between nanoscience and manufacturing. It also makes polymorphism control of functional materials a potential strategy for further improving supercapacitive output of metal oxides

Families of superhard crystalline carbon allotropes induced via cold-compressed graphite and nanotubes

We report a general scheme to systematically construct two classes of structural families of superhard sp3 carbon allotropes of cold compressed graphite through the topological analysis of odd 5+7 or even 4+8 membered carbon rings stemmed from the stacking of zigzag and armchair chains. Our results show that the previously proposed M, bct-C4, W and Z allotropes belong to our currently proposed families and that depending on the topological arrangement of the native carbon rings numerous other members are found that can help us understand the structural phase transformation of cold-compressed graphite and carbon nanotubes (CNTs). In particular, we predict the existence of two simple allotropes, R- and P-carbon, which match well the experimental X-ray diffraction patterns of cold-compressed graphite and CNTs, respectively, display a transparent wide-gap insulator ground state and possess a large Vickers hardness comparable to diamond.Comment: 5 pages, 4 figures, accepted by Phys. Rev. Let

Stabilization of hybrid stochastic differential equations by delay feedback control based on discrete-time observations

Response lags are necessary for most physical systems. For the sake of saving time and costs, the main aim of this paper is to design the feedback control term based on the response lags varying in a certain interval and the discrete-time observations of both the system states and the Markovian states to stabilize the controlled hybrid systems. The control principles are established, which permit the control function only depends on the partial information of the states and the modes. The upper bound on the sum of the upper bound Τ̅ of response lags, and the duration Ƭ between two consecutive observations is obtained. Some examples and numerical experiments are given to illustrate our theory