arXiv subjects

Yan-Ling Li

Publications and source records attributed to Yan-Ling Li.

34 records · Page 2Linked to original sources

arXiv2017

Protecting qutrit-qutrit entanglement by weak measurement and reversal

Entangled states in high dimensional systems are of great interest due to the extended possibilities they provide in quantum information processing. Recently, Sun et al. [Phys. Rev. A 82, 052323 (2010)] and Kim et al. [Nat. Phys. 8, 117 (2012)] pointed out that weak measurement and quantum weak measurement reversal can actively combat decoherence. We generalize their studies from qubits to qutrits under amplitude damping decoherence. We find that the qutrit-qutrit entanglement can be partially retrieved for certain initial states when only weak measurement reversals are performed. However, we can completely defeat amplitude damping decoherence for any initial states by the combination of prior weak measurements and post optimal weak measurement reversals. The experimental feasibility of our schemes is also discussed.

quant-ph↗

arXiv2017

Chiral-scale effective theory including a dilatonic meson

A scale-invariant chiral effective Lagrangian is constructed for octet pions and a dilaton figuring as Nambu-Goldstone bosons with vector mesons incorporated as hidden gauge fields. The Lagrangian is built to the next-to-leading order in chiral-scale counting without baryon fields and then to leading order including baryons. The resulting theory is hidden scale-symmetric and local symmetric. We also discuss some possible applications of the present Lagrangian.

hep-ph↗

arXiv2017

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.

quant-ph↗

arXiv2017

Strain engineering and photocatalytic application of single-layer ReS$_2$

We present a theoretical study on the electronic, dynamical, and photocatalytic properties of single-layer ReS$_2$ under uniaxial and shear strains. The single-layer ReS$_2$ shows strong anisotropic responses to straining. It remains dynamically stable for a wide range of $x$-axial strain, but becomes unstable for 2\% $y$-axial compressive strain. The single-layer ReS$_2$ is calculated to be an indirect bandgap semiconductor, and there is an indirect$-$direct bandgap transition under 1$-$5\% $x$-axial tensile straining. The single-layer ReS$_2$ is predicted incapable of catalyzing the water oxidation reaction. However, 1$-$5\% $y$-axial tensile strain can enable the single-layer ReS$_2$ for overall photocatalytic water splitting. Besides, the single-layer ReS$_2$ can also catalyze the overall water splitting and be most efficient under acidic water solutions with pH=3.8.

cond-mat.mtrl-sci↗

arXiv2016

Robust quantum state transfer between two superconducting qubits via partial measurement

We develop a potentially practical proposal for robust quantum state transfer (QST) between two superconducting qubits coupled by a coplanar waveguide (CPW) resonator. We show that the partial measurement could drastically enhance the fidelity even when the dissipation of qubits and CPW is considered. Unlike many other schemes for QST, our proposal does not require the couplings between the qubits and the CPW resonator to be strong. In fact, our method works much more efficiently in the weak coupling regime. The underlying mechanism is attributed to the probabilistic nature of partial measurement.

quant-ph↗

arXiv2016

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.

quant-ph↗

arXiv2016

Novel chemistry of lithium oxides and superconducting low-pressure LiO4

We study the stability of Li-O compounds as a function of pressure, with Li ion battery applications and fundamental chemical interest in mind. Using the ab initio evolutionary algorithm, we predict stability of novel compounds LiO4, Li5O3 and Li6O under pressure. LiO4, formed at the pressure of just 6 GPa, can be seen as ε-O8 accepting two electrons from two Li atoms. This phase is superconducting, with Tc up to 12.2 K at 10 GPa. This is remarkable, because elemental oxygen becomes superconducting at much higher pressure (96 GPa) and has much lower Tc (<0.6 K), and suggests that chemical alloying with other elements has the potential of not only decreasing metallization pressure, but also of increasing Tc. Since ε-O8 is called red oxygen, LiO4 can be identified "lithium red-oxid", and is distinct from superoxide. Additionally, Li5O3 is stable at pressures above 70 GPa and can be represented as a hybrid structure 4Li2O {\cdot} Li2O2, and electride suboxide Li6O is stable above 62 GPa.

cond-mat.mtrl-sci↗

arXiv2016

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.

quant-ph↗

arXiv2015

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.

quant-ph↗

arXiv2015

The electronic origin of shear-induced direct to indirect gap transition and anisotropy diminution in phosphorene

Artificial monolayer black phosphorus, the so-called phosphorene has attracted global interest with its distinguished anisotropic optoelectronic and electronic properties. Here, we unraveled the shear-induced direct to indirect gap transition and anisotropy diminution in phosphorene based on first-principles calculations. Lattice dynamic analysis demonstrated that phosphorene can sustain up to 10% applied shear strain. The band gap of phosphorene experiences a direct to indirect transition when 5% shear strain is applied. The electronic origin of direct to indirect gap transition from 1.54 eV at ambient condition to 1.22 eV at 10% shear strains for phosphorene was explored and the anisotropy diminution in phosphorene is discussed by calculating the maximum sound velocities, effective mass and decomposed charge density, which signals the undesired shear-induced direct to indirect gap transition in the applications of phosphorene for electronics and optoelectronics. On the other hand, the shear-induced electronic anisotropy properties suggest that phosphorene can be applied as the switcher in the nano electronic applications.

cond-mat.mtrl-sci↗

arXiv2015

Classical-driving-enhanced parameter-estimation precision of a non-Markovian dissipative two-state system

The dynamics of quantum Fisher information (QFI) of the phase parameter in a driven two-state system is studied within the framework of non-Markovian dissipative process. The influences of memory effects, classical driving and detunings on the parameter-estimation precision are demonstrated by exactly solving the Hamiltonian under rotating-wave approximation. In sharp contrast with the results obtained in the presence of Markovian dissipation, we find that classical driving can drastically enhance the QFI, namely, the precision of parameter estimation in the non-Markovian regime. Moreover, the parameter-estimation precision may even be preserved from the influence of surrounding non-Markovian dissipation with the assistance of classical driving. Remarkably, we reveal that the enhancement and preservation of QFI highly depend on the combination of classical driving and non-Markovian effects. Finally, a phenomenological explanation of the underlying mechanism is presented in detail via the quasimode theory

quant-ph↗

arXiv2015

Exotic stable calcium carbides: theory and experiment

It is well known that pressure causes profound changes in the properties of atoms and chemical bonding, leading to the formation of many unusual materials. Here we systematically explore all stable calcium carbides at pressures from ambient to 100 GPa using variable-composition evolutionary structure predictions. We find that Ca5C2, Ca2C, Ca3C2, CaC, Ca2C3, and CaC2 have stability fields on the phase diagram. Among these, Ca2C and Ca2C3 are successfully synthesized for the first time via high-pressure experiments with excellent structural correspondence to theoretical predictions. Of particular significance are the base-centered monoclinic phase (space group C2/m) of Ca2C, a quasi-two-dimensional metal with layers of negatively charged calcium atoms, and the primitive monoclinic phase (space group P21/c) of CaC with zigzag C4 groups. Interestingly, strong interstitial charge localization is found in the structure of R-3m-Ca5C2 with semimetallic behaviour.

cond-mat.mtrl-sci↗

arXiv2014

Strain Engineering for Phosphorene: The Potential Application as a Photocatalyst

Phosphorene has been attracted intense interest due to its unexpected high carrier mobility and distinguished anisotropic optoelectronic and electronic properties. In this work, we unraveled strain engineered phosphorene as a photocatalyst in the application of water splitting hydrogen production based on density functional theory calculations. Lattice dynamic calculations demonstrated the stability for such kind of artificial materials under different strains. The phosphorene lattice is unstable under compression strains and could be crashed. Whereas, phosphorene lattice shows very good stability under tensile strains. Further guarantee of the stability of phosphorene in liquid water is studied by ab initio molecular dynamics simulations. Tunable band gap from 1.54 eV at ambient condition to 1.82 eV under tensile strains for phosphorene is evaluated using parameter-free hybrid functional calculations. Appropriate band gaps and band edge alignments at certain pH demonstrate the potential application of phosphorene as a sufficiently efficient photocatalyst for visible light water splitting. We found that the strained phosphorene exhibits significantly improved photocatalytic properties under visible-light irradiation by calculating optical absorption spectra. Negative splitting energy of absorbed H2O indicates the water splitting on phosphorene is energy favorable both without and with strains.

cond-mat.mtrl-sci↗

arXiv2014

Pressure-induced Superconductivity in CaC2

Carbon can exist as isolated dumbbell, one-dimensional (1D) chain, 2D plane, and 3D network in carbon solids or carbon-based compounds, which attributes to its rich chemical binding way, including sp-, sp2-, and sp3-hybridized bonds. Sp2 hybridizing carbon always captures special attention due to its unique physical and chemical property. Here, using evolutionary algorithm in conjunction with ab initio method, we found that under compression, dumbbell carbon in CaC2 can be polymerized firstly into one-dimensional chain and then into ribbon and further into two dimensional graphite sheet at higher pressure. The C2m structure transforms into an orthorhombic Cmcm phase at 0.5 GPa, followed by another orthorhombic Immm phase, which is stabilized at wide pressure range of 15.2-105.8 GPa and then forced into MgB2-type phase with wide range stability up to at least 1 TPa. Strong electron-phonon coupling in cold compressed CaC2 is found, in particular for Immm phase, which has the highest lambda value (0.562-0.564) among them, leading to its high superconducting critical temperature (7.9~9.8 K), wihich is comparable to 11.5K value of CaC6. Our research results show that calcium can not only stabilize carbon sp2 hybridization at larger range of pressure but make them present superconducting behavior, which would further ignite experimental and theoretical research interests on Alkali-Earth metal carbides to uncover their peculiar physical properties under extreme conditions.

cond-mat.supr-con↗

arXiv2013

Formation of Nanofoam carbon and re-emergence of Superconductivity in compressed CaC6

Pressure can tune material's electronic properties and control its quantum state, making some systems present disconnected superconducting region as observed in iron chalcogenides and heavy fermion CeCu2Si2. For CaC6 superconductor (Tc of 11.5 K), applying pressure first Tc increases and then suppresses and the superconductivity of this compound is eventually disappeared at about 18 GPa. Here, we report a theoretical finding of the re-emergence of superconductivity in heavily compressed CaC6. The predicted phase III (space group Pmmn) with formation of carbon nanofoam is found to be stable at wide pressure range with a Tc up to 14.7 K at 78 GPa. Diamond-like carbon structure is adhered to the phase IV (Cmcm) for compressed CaC6 after 126 GPa, which has bad metallic behavior, indicating again departure from superconductivity. Re-emerged superconductivity in compressed CaC6 paves a new way to design new-type superconductor by inserting metal into nanoporous host lattice.

cond-mat.supr-con↗

arXiv2009

New potential super-incompressible phase of ReN$_{2}$

The structural, elastic, and electronic properties of ReN$_{2}$ are investigated by first-principles calculations with density functional theory. The obtained orthorhombic $Pbcn$ structure is energetically the most stable structure at ambient pressure. ReN$_{2}$ is a metallic, superincompressible solid and presents a rather elastic anisotropy. The estimated Debye temperature and hardness are 735 K and 17.1 GPa, respectively. Its estimated hardness is comparative to that of Si$_{3}$N$_{4}$.

cond-mat.mtrl-sci↗