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By solving the three-dimensional incompressible Reynolds-averaged Navier-Stokes equations, numerical simulations of the viscous flow within a flush type intake duct of a waterjet under different motion conditions are carried out. Therein, the effects of the steering and reversing unit as well as the impeller shaft on the flow field are taken into account. The numerical results show that the static pressure under backward conditions with the reversing jet flow is the lowest, and the cavitations are most likely to occur within the intake duct. The flow field under forward conditions is less uniform because of the shaft, while the velocity uniformity under backward conditions is improved. The shaft rotation causes an asymmetric secondary flow above the shaft under all conditions. The pressure contours under backward conditions with the reversing jet flow are sensitive to the presence of the shaft. This study can provide some references for the design optimization of waterjet propulsion system.

For the special ship like catamaran, which has a unique structure with gap resonance, the traditional potential method tends to over-predict the motion at the resonance frequency due to the neglige...

In this article, we propose an efficient quantum $k$ -collision search algorithm with low quantum memory $O(n)$ . The previous quantum $k$ -collision algorithms can not be converted into a low quantum memory $k$ -collision algorithm directly, because the time complexity of the converted algorithm is larger than the basic $k$ -collision algorithm. To solve this problem, we shall not only divide our low memory quantum $k$ -collision algorithm into several subroutines, but also need to achieve some balances between these subroutines. The time complexity of our $k$ -collision search algorithm is $\widetilde {O}\left({2^{\frac {(2^{k}-2)n}{2^{k+1}-3}}}\right)$ , and the classical memory and quantum memory complexities are $\widetilde {O}\left({2^{\frac {(2^{k-1}-1)n}{2^{k+1}-3}}}\right)$ and $O(n)$ respectively. In addition, we propose an efficient $k$ -claw search algorithm, which can output a $k$ -claw with $O(n)$ qubits. Given $2^{s}$ quantum processors, we can construct our quantum $k$ -collision and $k$ -claw parallel algorithm with the time of $\widetilde {O}\left({2^{\frac {(2^{k}-2)n-(2^{k+1}-2^{k-1}-3)s}{2^{k+1}-3}}}\right)$ , while the classical memory and quantum memory complexities are $\widetilde {O}\left({2^{\frac {(2^{k-1}-1)n+s\cdot 2^{k-2}}{2^{k+1}-3}}}\right)$ and $O(n)$ , respectively.

In this paper we address the issue of the interplay between non-Markovianity and nonclassicality of a system. We consider the action of non-Markovian environments on a qubit in terms of two models, a classical noise model and a quantum microscopic collision model. For both models we use the violation of the Leggett-Garg inequality (LGI) as a criterion of quantumness, and use the conditional past-future (CPF) correlation to measure non-Markovianity. Besides for the collision model, we also use violation of the nondiscord generating and detecting (NDGD) dynamics to indicate the nonclassicality. And LGI, NDGD, and CPF are probed sequentially by three projective measurements of some observable. In this paper we do not use the assumption of the quantum regression theorem and especially for the collision model the measurement backaction on the environment is explicitly considered. We find that compared with the Markovian dynamics the LGI can be violated for a longer time interval, i.e., non-Markovianity can preserve the quantumness of the system. For the collision model we find that for a specific measurement process, although the non-Markovianity cannot be detected, the effect of non-Markovianity of the system dynamics on nonclassicality still exists, and for some specific measurement operator the violation of both LGI and NDGD will never occur for the Markovian dynamics while with the enhancement of non-Markovianity the quantumness can appear. We also find that the NDGD can be violated for a much wider parameter regime than the LGI.

Radio-frequency interference (RFI) problems in modern electronic product become complex which result in the increasing number of scanning points. Conventional near-field phaseless source reconstruction methods such as double planes iteration method and single plane iteration method will spend a lot of time in both scanning and calculating. To save the calculating time and scanning time, an alternating iterative method is proposed for source reconstruction based on magnitude-only and single-plane near field scanning. Firstly, the single-plane scanning data is divided into two groups as group A and B according to the components, i.e. the electric field group and the magnetic field group for the four components, or ${H_{x}}$ group and ${H_{y}}$ group for two components. Then, the processed A and B phaseless data groups are used iteratively in the back-and-forth transformations to get the equivalent dipole elements. Under the premise of a large amount of scanning data, such as the simulation example, compared with conventional method filling the scanning data into a whole matrix, the proposed method can save 90% calculating time, especially the time in singular value decomposition (SVD) before the iteration. A numerical simulation and a measurement example is verified the effectiveness of the proposed method, which show a comprise between accuracy and efficiency.

The electronic states near the Fermi level of recently discovered superconductor ${\mathrm{Ba}}_{2}{\mathrm{CuO}}_{4\ensuremath{-}\ensuremath{\delta}}$ consist primarily of the Cu ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ and ${d}_{3{z}^{2}\ensuremath{-}{r}^{2}}$ orbitals. We investigate the electronic correlation effect and the orbital polarization of an effective two-orbital Hubbard model mimicking the low-energy physics of ${\mathrm{Ba}}_{2}{\mathrm{CuO}}_{4\ensuremath{-}\ensuremath{\delta}}$ in the hole-rich regime by utilizing the dynamical mean-field theory with the Lanczos method as the impurity solver. We find that the hole-overdoped ${\mathrm{Ba}}_{2}{\mathrm{CuO}}_{4\ensuremath{-}\ensuremath{\delta}}$ with $3{d}^{8}$ (${\mathrm{Cu}}^{3+}$) is in the orbital-selective Mott phase (OSMP) at half-filling, and the typical two-orbital feature remains in ${\mathrm{Ba}}_{2}{\mathrm{CuO}}_{4\ensuremath{-}\ensuremath{\delta}}$ when the electron filling approaches ${n}_{e}\ensuremath{\sim}2.5$, which closely approximates to the experimental hole doping for the emergence of the high-${T}_{c}$ superconductivity. We also obtain that the orbital polarization is very stable in the OSMP, and the multiorbital correlation can drive orbital polarization transitions. These results indicate that in hole-overdoped ${\mathrm{Ba}}_{2}{\mathrm{CuO}}_{4\ensuremath{-}\ensuremath{\delta}}$ the OSMP physics and orbital polarization, local magnetic moment, and spin or orbital fluctuations still exist. We propose that our present results are also applicable to ${\mathrm{Sr}}_{2}{\mathrm{CuO}}_{4\ensuremath{-}\ensuremath{\delta}}$ and other two-orbital cuprates, demanding an unconventional multiorbital superconducting scenario in hole-overdoped high-${T}_{c}$ cuprates.

We theoretically study the superconductivity in multiorbital superconductors based on a three-orbital tight-banding model. With appropriate values of the nearest-neighbour exchange $J_{1}^{\alpha \beta}$ and the next-nearest-neighbour exchange $J_{2}^{\alpha \beta}$, we find a two-dome structure in the $T_{c}-n$ phase diagram: one dome in the doping range $n, Comment: 16 pages, 6 figures

Poor interface bonding conditions reduce the bearing capacity of asphalt pavements and lead to several distresses. In particular, the association between localized interface debonding and near-surface longitudinal cracking was detected by field observations in the United States. Prediction of potential location and extent of localized interface debonding is important to preclude near-surface cracking. However, there is limited information regarding the onset of localized interface debonding induced by bending. Since interface debonding location and extent may depend on pavement structure, material properties, and loading conditions, a practical approach is needed. Several researchers adopted an equivalent elastic approach to overcome the complexity of modeling the viscoelastic responses of asphalt when evaluating the impact of multiple factors. Therefore, this study focused on determining whether the equivalent elastic approach can be used to identify the potential location of bending-induced localized interface debonding without a significant loss of accuracy. The viscoelastic and equivalent elastic analyses were conducted using 3-D finite element models developed to simulate an asphalt pavement subjected to a moving load. The 3-D equivalent elastic analysis appeared to be sufficient to accurately determine the potential location and extent of localized debonding induced by bending, which are mainly controlled by presence of shear stress in combination with low confinement on the horizontal interface plane. Furthermore, localized debonding was found to likely occur along a strip in the longitudinal direction which resembles a plane-strain problem. This study substantiated that future research efforts can focus on the transverse cross-section when assessing the impact of localized debonding.

Searching for spin liquids on the honeycomb J1-J2 Heisenberg model has been attracting great attention in the past decade. In this Paper we investigate the topological properties of the J1-J2 Heisenberg model by introducing nearest-neighbour and next-nearest-neighbour bond parameters. We find that there exist two topologically different phases in the spin disordered regime 0.20.32, it is a pi-flux chiral spin liquid, which is topological nontrivial and gapped. These results suggest that there exist two topologically different spin disorder phases in honeycomb J1-J2 Heisenberg model., Comment: 11 pages, 4 figures

An open question of fundamental importance in quantum thermodynamics is how to describe the statistics of work for initial state with quantum coherence. In this paper, work statistics is considered from a fully new perspective of "wave-particle" duality. Based on the generalized quantum work measurement, predictability of energy levels $\mathcal{D}_W$ and effectiveness of coherence $\mathcal{V}_W$ are defined, and they obey inequality $\mathcal{D}_W^2+\mathcal{V}_W^2\leq1$, which is the fundamental tradeoff relations between the contributions of population and coherence to quantum work distribution. As an application, we consider a driven two-level system and discuss the condition of the bound of above tradeoff relation. These results shed light on the effects of quantum coherence in quantum thermodynamics.

In this paper, an improved potential flow model is proposed for the hydrodynamic analysis of ships advancing in waves. A desingularized Rankine panel method, which has been improved with the added effect of nonlinear steady wave-making (NSWM) flow in frequency domain, is employed for 3D diffraction and radiation problems. Non-uniform rational B-splines (NURBS) are used to describe the body and free surfaces. The NSWM potential is computed by linear superposition of the first-order and second-order steady wave-making potentials which are determined by solving the corresponding boundary value problems (BVPs). The so-called mj terms in the body boundary condition of the radiation problem are evaluated with nonlinear steady flow. The free surface boundary conditions in the diffraction and radiation problems are also derived by considering nonlinear steady flow. To verify the improved model and the numerical method adopted in the present study, the nonlinear wave-making problem of a submerged moving sphere is first studied, and the computed results are compared with the analytical results of linear steady flow. Subsequently, the diffraction and radiation problems of a submerged moving sphere and a modified Wigley hull are solved. The numerical results of the wave exciting forces, added masses, and damping coefficients are compared with those obtained by using Neumann&ndash, Kelvin (NK) flow and double-body (DB) flow. A comparison of the results indicates that the improved model using the NSWM flow can generally give results in better agreement with the test data and other published results than those by using NK and DB flows, especially for the hydrodynamic coefficients in relatively low frequency ranges.

The Su--Schrieffer--Heeger (SSH) model is one of the simplest topological lattice models and is a promising candidate for quantum simulations of topological systems. In this study we investigate an interacting SSH model with nearest-neighbor interactions using mean field theory and an exact diagonalization method after the Jordan-Wigner transformation. We obtain a rich phase diagram with six different phases. Majorana bound states are found and confirmed by analyzing wave functions and Majorana number. In addition, we propose to use superconducting devices to construct a one-dimensional quantum circuit, where Cooper pair boxes and Josephson junctions are alternately connected in series, to theoretically simulate the interacting SSH model. This approach also provides us a toolkit to simulate correlated topological systems.

Different instabilities have been confirmed to exist in the three-dimensional (3D) electron gas when it is confined to the lowest Landau level in the extreme quantum limit. The recently discovered 3D topological semimetals offer a good platform to explore these phenomena due to the small sizes of their Fermi pockets, which means the quantum limit can be achieved at relatively low magnetic fields. In this work, we report the high-magnetic-field transport properties of the Dirac semimetal state in pressurized black phosphorus. Under applied hydrostatic pressure, the band structure of black phosphorus goes through an insulator-semimetal transition. In the high pressure topological semimetal phase, anomalous behaviors are observed on both magnetoresistance and Hall resistivity beyond the relatively low quantum limit field, which is demonstrated to indicate the emergence of an exotic electronic state hosting a density wave ordering. Our findings bring the first insight into the electronic interactions in black phosphorus under intense field.

We present the modulation of magnetic order on the orbital selective Mott phases (OSMP) and the metal-insulator transitions (MIT) of multi-orbital Hubbard models by employing the rotationally invariant slave-boson methods. We show that at half filling, the well-known paramagnetic (PM) OSMP is completely covered by an antiferromagnetic (AFM) Slater insulator, and the PM Mott phase by an AFM Mott insulator when electron correlation strength varies from intermediate to strong both in two- and three-orbitals Hubbard systems. Away from half-filling, we find that a partial-polarized AFM orbital-selective Slater phase appears in the intermediate correlation regime, and an almost full-polarized AFM OSMP fully covers the paramagnetic OSMP. In addition, the ferromagnetic phase in the three-orbital case is more robust than that in the two-orbital case. These results demonstrate that the modulation of magnetic correlation to the quasiparticle spectra leads to much rich and more interesting MIT scenario in multiorbital correlated systems.

In this paper, we present the electronic and magnetic properties of the ferromagnetic semiconductor Cr2Si2Te6 doped by charge particles by the first-principles calculations. We find that doped Cr2Si2Te6 manifests a ferromagnetic metallic phase and its Curie temperature significantly increases from 54 to 125 K, as well as the magnetic coupling changing from weak super-exchange to strong double-exchange interaction. Moreover, the magnetic easy axis in doped Cr2Si2Te6 rotates from the ⟨001⟩ direction to the ab-plane. Our results provide an easily accessible method to considerably increase the ferromagnetic transition temperature of van der Waals crystals.

By using the adaptive measurement method we study how to detect whether a weak magnetic field is actually present or not under Gaussian noise and non-Gaussian noise. We find that the adaptive measurement method can effectively improve the detection accuracy. For the case of Gaussian noise, we find the stronger the magnetic field strength, the easier for us to detect the magnetic field. Counterintuitively, for non-Gaussian noise, some weaker magnetic fields are more likely to be detected rather than some stronger ones. Finally, we give a reasonable physical interpretation.

Effects of longitudinal ( J Z ) and transverse (including spin-flip J X and pair-hopping J P terms) Hund’s couplings on Mott transitions of two-orbital Hubbard models are studied by the rotationally invariant slave boson approach. We show that in the half-filled asymmetric systems, the orbital selective Mott phase (OSMP) expands with increasing J X , P / J Z when J X , P / J Z 1 , and has the largest region in the isotropic case ( J X , P / J Z = 1 ); and further increasing spin-flip Hund’s coupling to J X , P / J Z > 1 may quickly suppress the OSMP state. In other near-half-filled systems, the transverse Hund’s coupling favors or unfavors the OSMP state, depending on the electronic correlation strength of the systems. In the quarter-filled and around systems, a small J X , P / J Z 1 has less effect on Mott transition, while a large J X , P / J Z > 1 enhances the electron itineracy and considerably increases the critical correlation strength of the Mott transition both in symmetric and asymmetric systems. These results could be addressed by different spin–orbital states favored by J X , J P and J Z components, respectively; and the competing longitudinal and transverse Hund’s coupling terms lead to most strong quantum fluctuations in the isotropic system.

The motions of ice floes in linear waves were simulated by coupling Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD). The interactions between ice floes are investigated by DEM. The hydrodynamics of ice floes, mainly including the drag force and the buoyancy, are calculated by CFD. In the simulation, the ice floes are treated as discrete elements, and the contact forces between ice floes are determined by the Hertz-Mindlin (no-slip) contact model. The shape of ice floes is an approximate square composed of a number of spherical faces, which can reduce the computation cost. The waves are treated as First Order Airy wave, which is linear in nature and applied to small amplitude waves in shallow liquid depth ranges. The volume of fluid (VOF) method was adopted to capture the free surface. The simulation results are in agreement with the actual situation to a certain extent.

To investigate the role of initial quantum coherence in work-probability distribution, it is necessary to consider an incomplete or partial measurement, in which the energy cannot be fully discriminated by the detector. In this paper, we use a harmonic oscillator with a coherent or squeezing state to realize this incomplete or partial measurement, and propose a unified framework of quantum work statistics for a closed system with an arbitrary initial state. We find that work is proportional to the change of the real part of the coherent state parameter, i.e., quantum work can be estimated by the coherent state parameter. The resulting work-probability distribution includes the initial quantum coherence, and can be reduced to the result of the traditional two projective energy measurement scheme (TPM) by squeezing the state of the harmonic oscillator. Our measurement scheme reveals the fundamental connections between measurement error and coherent work. By introducing a ‘coherent work-to-noise ratio’, we find the optimal measurement error, which is determined by the energy difference between the superposed energy levels. As an application, we consider a driven two-level system and investigate the effects of driving velocity on work statistics. We find that only when the driving velocity matches the transition frequency of the system can initial quantum coherence play an important role.

The influence of Gaussian noise on weak values is studied. A general expression of weak values is derived, which is applicable to both Markovian and non-Markovian environment. Weak values under random telegraph noise and the colored noise of type 1 / f a are investigated in particular, and the properties of weak values under those non-Gaussian noises are discussed. Furthermore, the threshold time for weak values keeping its characteristic to exceed spectrum range is found, which can reach a large value by the memory effect of non-Markovian environment.

Spin chains are promising candidates for quantum communication and computation. Using quantum optimal control (OC) theory based on the Krotov method, we present a protocol to perform quantum state transfer with fast and high fidelity by only manipulating the boundary spins in a quantum spin-1/2 chain. The achieved speed is about one order of magnitude faster than that is possible in the Lyapunov control case for comparable fidelities. Additionally, it has a fundamental limit for OC beyond which optimization is not possible. The controls are exerted only on the couplings between the boundary spins and their neighbors, so that the scheme has good scalability. We also demonstrate that the resulting OC scheme is robust against disorder in the chain.

We theoretically study the coexistence of spin density wave (SDW) and superconductivity (SC) in ironpnictide superconductors based on a three-orbital model, focusing on the momentum-space and real-space distributions of SDW and SC order parameters in the coexistence region. We show that a SDW–SC coexisting state lies in the T–n phase diagram, in qualitative agreement with those of NaFe1 − xCoxAs and Ba(Fe1 − xCox)2As2. In the SC state the pairing wavefunction has s ± symmetry with s x 2 y 2 and s x 2 + y 2 components. In the coexisting state, the SDW and SC order parameters display strong orbital-selective competitions in momentum space, which also result in real-space modulation and spin singlet–triplet mixing in the Cooper pairing amplitude. We expect that the obtained features may be observed in future experiments.

The dynamics of N -qubit GHZ state quantum Fisher information (QFI) under phase noise lasers (PNLs) driving is investigated in terms of non-Markovian master equation. We first investigate the non-Markovian dynamics of the QFI of N -qubit GHZ state and show that when the ratio of the PNL rate and the system–environment coupling strength is very small, the oscillations of the QFIs decay slower which corresponds to the non-Markovian region; yet when it becomes large, the QFIs monotonously decay which corresponds to the Markovian region. When the atom number N increases, QFIs in both regions decay faster. We further find that the QFI flow disappears suddenly followed by a sudden birth depending on the ratio of the PNL rate and the system–environment coupling strength and the atom number N , which unveil a fundamental connection between the non-Markovian behaviors and the parameters of system–environment couplings. We discuss two optimal positive operator-valued measures (POVMs) for two different strategies of our model and find the condition of the optimal measurement. At last, we consider the QFI of two atoms with qubit–qubit interaction under random telegraph noises (RTNs).

We investigate the quantum speed limit (QSL) time of an electronic spin coupled to a bath of nuclear spins. We consider three types of initial states with different correlations between the system and bath, i.e., quantum correlation, classical correlation, and no any correlation. Interestingly, we show that the QSL times of the central spin for these three types of initial correlations are identical when the couplings are homogeneous. However, it is remarkable different for inhomogenous couplings. The QSL time of the central spin is sensitive to the initial states, the average coupling strength, the distribution of the couplings between the system and bath and the number of the nuclear spins in the bath. Furthermore, we find that the coherence in the initial state has significant influences on the QSL time of the system, and can lead to the increase of QSL time for homogeneous couplings.

We consider a composite system: an anisotropic two-qubit Heisenberg XY Z chain coupled independently to their own environments. We take one of the qubit as the subsystem and the other qubit as an auxiliary qubit, and then the subsystem we concern can be considered to be coupled to a structured bath (auxiliary qubit + environments). Based on this, we study the non-Markovianity of the subsystem dynamics and show how the subsystem dynamics can be changed by manipulating the intensity of the qubit-qubit couplings or the anisotropy parameter. Moreover, we show how entanglement between the subsystem and the structured bath can be affected by the properties of the structured bath and the magnetic field.

We study the speed-up role of dynamical decoupling in an open system, which is modeled as two central spins coupled to their own XY spin-chain environment. We show that the fast bang–bang pulses can suppress the system evolution, which manifests the quantum Zeno effect. In contrast, with the increasing of the pulse interval time, the bang–bang pulses can enhance the decay of the quantum speed limit time and induce the speed-up process, which displays the quantum anti-Zeno effect. In addition, we show that the random pulses can also induce the speed-up of quantum evolution.

Based on conditional past&ndash, future (CPF) correlations, we study the non-Markovianity of a central spin coupled to an isotropic Lipkin&ndash, Meshkov&ndash, Glick (LMG) bath. Although the dynamics of a system is always non-Markovian, it is found that some measurement time intervals considering a specific process, with respect to a particular set of CPF measurement operators, can be zero, which means that in this case the non-Markovianity of the system could not be detected. Furthermore, the initial system&ndash, bath correlations only slightly influence the non-Markovianity of the system in our model. Significantly, it is also found that the dynamics of the system for LMG baths, initially in the ground states corresponding to the symmetric phase and symmetry broken phase, exhibit different properties, and the maximal value of the CPF at the critical point is the smallest, independent of the measurement operator, which means that the criticality can manifest itself by the CPF. Moreover, the effect of bath temperature on the quantum criticality of the CPF depends on the measurement operator.

Effects of electronic correlation and spin-orbit coupling (SOC) on electronic structure of iron selenides (${\mathrm{Li}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}$)OHFeSe have been investigated with the combination of density functional theory (DFT) and dynamical mean-field theory. It is found that the electronic correlation substantially changes the Fermi surface topology for $x=0.2$, resulting in a tiny electron pocket around the zone center $\mathrm{\ensuremath{\Gamma}}$ and two large electron pockets around the zone corner $M$, respectively. Moreover, the SOC also considerably affects the low-energy electronic structure near the Fermi level, especially inducing a gap in the Dirac-like dispersion around $\mathrm{\ensuremath{\Gamma}}$ for $x=0.2$. Our calculations show a correlation-driven Lifshitz transition from FeSe to the heavily electron-doped compound, leading to a transition of the nesting wave vector from ($\ensuremath{\pi}$, 0) to ($\ensuremath{\pi}$, $0.5\ensuremath{\pi}\ifmmode\pm\else\textpm\fi{}\ensuremath{\delta}$) accompanied by an orbital-weight redistribution between the ${d}_{xy}$ and ${d}_{xz}/{d}_{yz}$ orbitals. These correlation-driven electronic structures enrich the understanding of different DFT and experimental results, suggesting a quite distinct superconducting state of (${\mathrm{Li}}_{0.8}{\mathrm{Fe}}_{0.2}$)OHFeSe in comparison with FeSe.

We propose schemes to entangle two quantum dots (QDs) with the aid of Majorana fermions via optimal control. Two paradigmatic cases, the teleportation and the intradot spin flip processes, are considered, respectively, in the charge and spin degrees of QDs. We demonstrate that optimal control techniques can be effectively used to prepare entanglement between two QDs through manipulating their chemical potentials. Significantly, our optimal control generation of entangled states has a prominent advantage: The runtime is much shorter than in adiabatic passage, providing a shortcut to adiabatic entanglement preparation.

We investigate the quantum speed limit (QSL) time of the central qubit coupled with a thermodynamic Ising spin chain. The external bang–bang (BB) pulse control is applied on the model. We show that the evolution speed of the central system can be enhanced by the BB pulse. Meanwhile, the influence from magnetic field and temperature of bath are also studied, and we find that for the situation of strong external field or low temperature the evolution speed of system can be accelerated. Besides these, the function of the sizes of environment is exhibited in our work and we discover the effect from the qubits numbers of bath on QSL time depends on the coupling strength between central system and bath spins.

We employ the self-consistent Bogoliubov-de Gennes (BdG) formulation to investigate the effect of single interstitial nonmagnetic/magnetic impurity in iron-based superconductors with s ± -wave pairing symmetry. We find that both the nonmagnetic and magnetic impurities can induce bound states within the superconducting (SC) gap and a π phase shift of SC order parameter at the impurity site. However, different from the interstitial-nonmagnetic-impurity case characterized by two symmetric peaks with respect to zero energy, the interstitial magnetic one only induces single bound-state peak. In the strong scattering regime this peak can appear at the Fermi level, which has been observed in the recent scanning tunneling microscope (STM) experiment of Fe(Te,Se) superconductor with interstitial Fe impurities (Yin et al. 2015 [44]). This novel single in-gap peak feature also distinguishes the interstitial case from the substitutional one with two peaks. These results provide important information for comparing the different impurity effects in the iron-based superconductors.

The radiation and the diffraction of a ship with a forward speed are studied by using a time domain Rankine panel method. The free surface conditions are linearized onto an undisturbed free surface based on the double body flow. The linearized body boundary condition is applied on the mean wetted hull surface. The fluid domain boundary is discretized by a collection of quadric panels. The unknown quantities, including the free surface elevation, the normal flux over the free surface and the potential on the fluid domain boundary, are determined at each time step. The numerical results are compared with experimental data and other numerical solutions, showing satisfactory agreements.

We investigate the entanglement dynamics of two electronic spins coupled to a bath of nuclear spins for two special cases, one is that two central spins both interact with a common bath, and the other is that one of two spins interacts with a bath. We consider three types of initial states with different correlations between the system and the bath, i.e., quantum correlation, classical correlation, and no-correlation. We show that the initial correlations (no matter quantum correlations or classical correlations) can effectively avoid the occurrence of entanglement sudden death. Irrespective of whether both two spins or only one of the two spins interacts with the bath, the system can gain more entanglement in the process of the time evolution for initial quantum correlations. In addition, we find that the effects of the distribution of coupling constants on entanglement dynamics crucially depend on the initial state of the spin bath.

We develop a generalized numerical optimization algorithm for the rotationally invariant multi-orbital slave boson approach, which is applicable for arbitrary boundary constraints of high-dimensional objective function by combining several classical optimization techniques. After constructing the calculation architecture of rotationally invariant multi-orbital slave boson model, we apply this optimization algorithm to find the stable ground state and magnetic configuration of two-orbital Hubbard models. The numerical results are consistent with available solutions, confirming the correctness and accuracy of our present algorithm. Furthermore, we utilize it to explore the effects of the transverse Hund’s coupling terms on metal–insulator transition, orbital selective Mott phase and magnetism. These results show the quick convergency and robust stable character of our algorithm in searching the optimized solution of strongly correlated electron systems.

We propose a scheme to synthesize atom---photon hybrid controlled-not (CNOT) gate by combining atomic single-qubit operations via stimulated Raman adiabatic passage and photonic Faraday rotation in cavity QED system. Benefiting from its hybrid characteristic, we utilize atom---photon CNOT gate to construct quantum CNOT gate for remote atoms and photons, respectively. As our scheme works in the bad cavity regime and only involves virtual excitation of atoms, it may be robust against both cavity decay and atomic spontaneous emission, thus can be realized with less demanding technology than that previously mentioned.

We investigate the influences of non-Markovian dissipation and global dephasing process on the dynamical behaviors of global discord among four qubits. We find that for the non-Markovian dissipation model W state is the most robust to decoherence compared to Dicke and GHZ states; however, for the global dephasing model Dicke state is the most robust to decoherence among them. Also the dynamical behaviors of global quantum discord are quite different from that of the multipartite entanglement for the non-Markovian dissipation model, while they are very similar to each other for the global dephasing model.

Quantum frequency estimation under general noise is investigated in the Bayesian parameter estimation approach. To evaluate the accuracy of estimation, the Bayes cost is obtained analytically which can be applied to the common noisy channels, such as the phase-damping channel, the amplitude-damping channel, and the depolarizing channel. The Bayes cost formula clearly shows that the prior information imposes a restriction upon the effect of noise in the estimation process. Three examples of frequency estimations are provided to illustrate the roles of prior probability in the estimation process. It is found that, due to the restriction of prior information on the noise, the estimation accuracy is less sensitive to the noise in the Bayesian approach than that in the Cram\'er-Rao bound approach. More prior information can help us to use the non-Gaussianity of the noise channel to improve the estimation accuracy in the phase-damping channel.

In this paper, we present the electronic structures and orbital-resolved electronic properties of structurally distorted $1T\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ bulk and monolayer within density functional theory approaches. The relaxed commensurate-charge-density-wave (CCDW) structure shows that 13 Ta atoms condense into a star-of-David cluster, accompanied by a buckling of neighboring $S$ planes. Through detailed analyses to the orbital characters near the Fermi level, we show that there exists an orbital-density-wave (ODW) order, which is predominantly contributed by Ta-$5{d}_{3{z}^{2}\ensuremath{-}{r}^{2}}$ orbital in the central Ta of the star-of-David cluster. We further demonstrate that the structural distortion, together with the Coulomb interaction, stabilizes the CCDW insulating ground state with an ODW order. The results obtained from dynamical mean-field theory confirm the role of the electronic correlation. Moreover, such an ODW ground state favors an intralayer ferromagnetic order in bulk and monolayer $1T\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$, and an interlayer antiferromagnetic order in bulk. We propose that $1T\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ monolayer may pave new ways to study exciton physics, flat-band physics, and potential applications in luminescence.

We investigate the heat transport between two nonthermal reservoirs based on a microscopic collision model. We consider a bipartite system consisting of two identical subsystems, and each subsystem interacts with its own local reservoir, which consists of a large collection of initially uncorrelated ancillas. Then a heat transport is formed between two reservoirs by a sequence of pairwise collisions (inter-subsystem and subsystem-local reservoir). In this paper we consider two kinds of reservoir's initial states, the thermal state, and the state with coherence whose diagonal elements are the same as that of the thermal state and the off-diaganal elements are nonzero. In this way, we define the effective temperature of the reservoir with coherence according to its diagonal elements. We find that for two reservoirs having coherence the direction of the steady current of heat is different for different phase differences between the two initial states of two reservoirs, especially the heat can transfer from the "cold reservoir" to the "hot reservoir" in the steady regime for particular phase difference. And in the limit of the effective temperature difference between the two reservoirs $\Delta T\rightarrow0$, for most of the phase differences, the steady heat current increases with the increase of effective temperature until to the high effective temperature limit; while for the thermal state or particular phase difference the steady heat current decreases with the increase of temperature at high temperatures, and in this case the conductance can be obtained.

The radical pair (RP) based compass is considered as one of the principal models of avian magnetoreception. Different from the conventional approach where the sensitivity of RP based compass is described by the singlet yield, we introduce the quantum Fisher information (QFI), which represents the maximum information about the magnetic field’s direction extracted from the RP state, to quantify the sensitivity of RP based compass. The consistency between our results and experimental observations suggests that the QFI may serve as a measure to describe the sensitivity of RP based compass. Besides, within the framework of quantum metrology, we give two specific possible measurement schemes and find that the conventional singlet yield is corresponding to the measurement of total angular momentum. Moreover, we show that the measurement of fluctuation of the total magnetic moment is much more accurate than the singlet yield measurement, and is close to the optimal measurement scheme. Finally, the effects of entanglement and decoherence are also discussed in the spirit of our approach.

We propose a quantum collision model in which the environment is abstractively divided into two hierarchies including "environment-bus" that has direct interactions with the system and "environment-stations" that has not. Based on the model, we investigate the effects of initial system---environment correlations, initial states of environment, and various interactions on the dynamics of open quantum systems associated genuinely with such a hierarchical environment. We illustrate that the initial quantum correlation between the system and environment leads to a transition from Markovian to non-Markovian dynamics, while for initial classical correlation the transition can only be confirmed to happen when the couplings rather than the correlations in environment are present. In addition, we investigate the degree of non-Markovianity varying with environment initial states and reveal that the interaction strength between two environmental hierarchies plays an important role in it. In particular, we show that in such a hierarchically structured environment the degree of non-Markovianity is not equivalent to memory effects of the environment-stations as a reservoir due to the presence of the environment-bus.