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Optimal two-qubit operation is of significance to quantum information processing. An efficient scheme is proposed for realizing the shortcut to adiabatic two-qubit state swap in a superconducting circuit quantum electrodynamics (QED) via effective drivings. Two superconducting qutrits are coupled to a common cavity field and individual classical drivings. Based on two Gaussian-type Rabi drivings, two-qubit state swap can be adiabatically implemented within a reduced three-state system. To speed up the operation, these two original Rabi drivings are modified in the framework of shortcuts to adiabaticity, instead of adding an extra counterdiabatic driving. Moreover, owing to a shorter duration time, the decoherence effects on the accelerated quantum operation can be mitigated significantly. The strategy could offer an optimized method to construct fast and robust quantum operations on superconducting qubits experimentally.

In 2016, Li et al. [Int. J. Theor. Phys. 55, 1820–1823 (2016)] proposed schemes for quantum teleportation of certain class of three and four qubit states by utilizing four- and five- qubit cluster states, respectively, as the quantum channels. Moreover, their teleportation-schemes necessitates multi-qubit entangled states. In the present study, it has been demonstrated that these authors committed trivial errors while designing their teleportation schemes and, hence, quantum teleportation could not be perfectly achieved. It is seen that the tasks of teleporting aforementioned class of three and four qubit states can be accomplished by applying only a two-qubit maximally entangled states, i.e., single Bell state as the quantum channel. It is, therefore, an improvement on Li et al. teleportation-schemes is proposed, which not only reduces quantum resource consumption but also operation complexity.

The interaction between two modes quantized field and asymmetric two atoms represents one of the important quantum models to study the nonclassical quantized phenomena. The two modes multiphoton processes and interacting asymmetric two two-level atoms are introduced in the proposed quantum system. The time dependent solution of the proposed quantum system is computed analytically for asymmetric and symmetric cases. This analytical solution depends on the eigenvalues and the eigenvectors of the coefficient matrix of the Schrodinger equation. The nonclassical features of the proposed quantum system are evaluated as the entanglement and the atomic populations. The entanglement between atom and field is measured via the von Neumann entropy while the entanglement between two atoms is measured by the concurrence. These quantized features are analyzed for variety of the detuning parameter, the atom-atom coupling constant, and the numbers of two photon modes. The most important observations are that: If the numbers of two photon modes are identical, the von Neumann entropy is strong most of the time, the periodic time of the entropy and atomic populations is double comparing with other cases, and the concurrence is non-existent for asymmetric case. In the presence the detuning parameter and the atom-atom coupling constant, the von Neumann entropy increases with time while the amplitude of the concurrence decreases with time for symmetric case. The fluctuations of the von Neumann entropy for symmetric case are stable and uniform more than its for asymmetric case. The concurrence is irregular for asymmetric case. Furthermore, there are other quantized effects of the proposed model which are discussed for symmetric and asymmetric cases.

In this paper, we use exact matrix diagonalization to research property of the many-body localization (MBL) in the disordered Heisenberg XXX model with periodic driving. We get the periodic time-dependent external field by trigonometric function, which is added to periodically drive this model. It is demonstrated that the fidelity of eigenstate is able to capture quantum criticality underlying many-body physics (Zhou et al. Phys. Rev. Lett. 100, 080601, 2008, Zhou and Barjaktarevi J. Phys. A: Math. Theor. 41, 412001 2008), which can be used to characterize the many-body localization transition in this closed spin system (Zanardi and Paunkovic Phys. Rev. E 74, 031123, 2006). We obtain the fidelity for high-energy many-body eigenstates, namely, the excited state fidelity, which shows the phase transition of periodically driven Heisenberg XXX chain with different disordered external field strengths and different system sizes. It is demonstrated that when Heisenberg XXX system is in a very small disorder, periodic driving can cause the occurrence of a transition from ergodic phase to MBL phase. In contrast to the HS model which has global two-body interaction, which we have studied recently with the same situation, there is no MBL phase transition when we drive the HS model in ergodic phase with periodic driving. It also shows that for the strong disordered Heisenberg XXX system, there will exist a critical driving period Tc, when driving period T is higher than Tc, the system will undergo a transition from localized phase to ergodic phase and the MBL phase will be broken. Furthermore, we discover that the size of the system and the strength of disorder will affect the critical point of driving period and the magnitude of the phase change. For the same system, the critical point increases as the strength of disorder increases. We also explore the non-disorder system of HS model with the same driving to explore the properties of MBL, it shows that under periodic driving, the non-disordered HS system has the quantum phase transition rather than MBL phase transition. This illustrates the important role of disorder on MBL.

We extend the standard solid-state quantum mechanical Hamiltonian containing only Coulomb interactions between the charged particles by inclusion of the (transverse) current-current diamagnetic interaction starting from the non-relativistic QED restricted to the states without photons and neglecting the retardation in the photon propagator. This derivation is supplemented with a derivation of an analogous result along the non-rigorous old classical Darwin-Landau-Lifshitz argumentation within the physical Coulomb gauge.

In this paper, we investigate the entanglement of a quantum system containing two subsystems characterized by the angular momenta j1 and j2, in the framework of the superposition of spin coherent states. We formulate the measure of the entanglement in terms of the amplitudes of the spin coherent states as well as their spins j1 and j2. We extend this investigation to rank-two bipartite mixed states involving spin-j coherent states by using a simplified expression of concurrence. We show that the bipartite entanglement of mixed states is strongly dependent on the spin ji of each subsystem and the probabilities associated with it.

We study the interatomic energy and force of two ground-state atoms in interaction with the fluctuating quantum massless scalar field in vacuum with two different approaches, i.e. the stationary perturbation theory and the DDC formalism [the formalism proposed by Dalibard, Dupont-Roc and Cohen-Tannoudji]. With the DDC formalism, we calculate the interatomic energy in terms of the contributions of vacuum fluctuations and the contributions of the atomic radiation reaction. We find that, in the near region, the contributions of vacuum fluctuations is less important than the contributions of the atomic radiation reaction, and as a result, the interatomic force is attractive and proportional to L− 3. While in the far zone, the contributions of vacuum fluctuations and those of the atomic radiation reaction become equally important, and the interatomic force is attractive and proportional to L− 4. The interatomic energy and force derived with these two different approaches are accurately the same. We comment that the two different approaches deal with the interatomic interaction from different perspectives and have their own advantages.

The exploration of quantum entanglement in multipartite quantum systems is of great significance to the study of quantum entanglement, maximally multi-qubit entangled state is one of the research objects. Recently, Che et al. presented a recurrence relation of multi-qubit state. According to this inspiration, we present the recurrence relation of maximally multi-qubit pure states of N-qubits for N = 6, 7, 8. Further, some new forms of the seven- and eight-qubit maximally entangled states are found with the recurrence relation.

We consider entangled state production utilizing a full optomechanical arrangement, based on which we create entanglement between two far three-level V-type atoms using a quantum repeater protocol. At first, we consider eight identical atoms (1; 2;...; 8), while adjacent pairs (i; i + 1) with i = 1; 3; 5; 7 have been prepared in entangled states and the atoms 1, 8 are the two target atoms. The three-level atoms (1,2,3,4) and (5,6,7,8) distinctly become entangled with the system including optical and mechanical modes by performing the interaction in optomechanical cavities between atoms (2,3) and (6,7), respectively. Then, by operating appropriate measurements, instead of Bell state measurement which is a hard task in practical works, the entangled states of atoms (1,4) and (5,8) are achieved. Next, via interacting atoms (4,5) of the pairs (1,4) and (5,8) and operating proper measurement, the entangled state of target atoms (1,8) is obtained. In the continuation, entropy and success probability of the produced entangled state are then evaluated. It is observed that the time period of entropy is increased by increasing the mechanical frequency and by decreasing optomechanical coupling strength to the field modes. Also, in most cases, the maximum of success probability is increased by decreasing G and via decreasing.

Quantum correlations are physical resources for quantum information processing. The nonlocal advantage of quantum coherence (NAQC) is a kind of quantum correlation which is stronger than entanglement. We report here methods for enhancing thermal NAQC in the two-site, triangular, and tetrahedral lattices. It is found that for all the considered cases, the NAQC can be noticeably enhanced by introducing the Dzyaloshinsky-Moriya (DM) interaction to two spins and tune the anisotropy of the spin-spin coupling. Besides, the critical temperature below which the thermal NAQC exists can also be noticeably enhanced by introducing the DM interaction. Hence, our results provide a way to achieve NAQC for quantum tasks based on spin lattices.

We present a theoretical study on quantum breathers in a XXZ Heisenberg ferromagnet with the single-ion uniaxial anisotropy on a two-dimensional hexangular lattice. In our work, the full quantum and the semiclassical cases are considered, respectively. For the full quantum case, we find that some isolated two-magnon bands can exist below the free magnon band. Physically, each isolated two-magnon band correspond to a two-magnon bound state, which is the simplest quantum breather state. For the semiclassical case, the analytical form of the discrete breather solution with a line localized structure is obtained by adopting the Glauber’s coherent-state representation. Furthermore, the influence of the anisotropy on the properties of quantum breathers is discussed in detail.

In this work, we give an analytical derivation of the reduced density matrix between two qubits in a cavity field, which is described by the quantum Rabi model. Using the coherent state method and the generalized hypergeometric functions, we find a complete solution of the 4-by-4 reduced density matrix for each eigen energy by taking the partial trace over the cavity field states. Four kinds of measurements used to describe the quantum entanglement and quantum correlation between the two qubits, i.e., the concurrence, quantum discord, steerable weight, and robustness of coherence, are calculated for the ground state and excited states. For both the weak coupling ( $g\rightarrow 0$ ) and deep-strong coupling ( $g\rightarrow \infty $ ) regimes, quantum entanglement and quantum correlation between the two qubits are vanishing. An appropriate coupling in the deep strong coupling regime between the qubits and the cavity field is required if one wants to establish quantum entanglement between the qubits.

Based on quantum renormalization group (QRG) method, we investigated quantum coherence and quantum phase transition (QPT) in XXZ chain and XY chain, respectively. The results show that both the geometric quantum coherence and entropic coherecne can accurately indicate the QPT at critical point after enough iteration steps. Moreover, the increasing anisotropy parameter destroys the coherence in the XXZ chain, while enhances it in the XY chain. In addition, focused on the XXZ chain we analyzed the nonanalytic phenomena and scaling behaviors with different theoretical exponents in detail.

We investigate the dynamical behaviors of quantum-memory-assisted entropic uncertainty relation (QMA-EUR) and quantum correlation (both quantum entanglement and quantum discord) for a two-qubit system coupled to a spin environment by a z–x-type interaction. Our purpose is to find out how the QMA-EUR and quantum correlations are affected by the pre-designed factors of the environment, including initial spin environmental states and the coupling constants. The numerical results show that the initial environmental state has significant effect on the dynamics of quantum correlations of the central spin system. We find that the environment should be prepared in a block entangled state with Bell state. This option is beneficial to reducing entropic uncertainty and inhibits the damping of quantum correlation. We also find that the high frequency particles in a spin bath can significantly enhance the robustness of quantum correlation of the system.

We investigate the dynamical behaviors of quantum-memory-assisted (QMA) entropic uncertainty for the central two-qubit system coupled to the N-site spin XY chain environment with z-component Dzyaloshinsky-Moriya (DM) interaction and external magnetic field, asymmetrically. The results show that the dynamics of QMA entropic uncertainty for a pair of Pauli observables are oscillatory and ascending gradually with evolution time, which is anti-correlated to the entanglement of the two-qubit system. We also find that QMA entropic uncertainty exhibits sudden change phenomena near the critical point of quantum phase transform both in the case of weak and strong coupling regimes, which can act as a new witness of the critical point of quantum phase transition. Meanwhile, the DM interactions of the spin chain environment have non-equivalent effects on the QMA entropic uncertainty when the external magnetic field strength is far from the critical point. Furthermore, the asymmetricallity of the qubit-environment couplings has slightly effects on QMA entropic uncertainty in the case of strong coupling regime of the two-qubit system. While, in the weak coupling regime of the two-qubit system, QMA entropic uncertainty is very sensitive to the asymmetricallity of qubit-environment couplings. Finally, the larger the number of spin sites of the environment, the more quickly the QMA entropic uncertainty increases to the maximal value both in the weak and strong coupling regimes of the two-qubit system.

Recently, Chen et al. [Int. J. Theor. Phys. 59, 1402–1412 (2020)] proposed a theoretical scheme for controlled quantum teleportation (CQT) of a Bell state by using seven-qubit entangled state as a quantum channel. In this comment, it is shown that the consumption of both the quantum and classical resources used by Chen et al. is excessively high because the actual task of CQT of a Bell state via seven-qubit entangled state can be reduced to the CQT of an arbitrary single-qubit state via three-qubit GHZ state. Hence, in this work, an improved scheme for CQT has been presented. We have also shown that the CQT of certain class of N-qubit entangled state can also be realized successfully by using a three-qubit GHZ state as the quantum channel. The intrinsic efficiency of the present communication scheme is very large as compared to that proposed by Chen et al.

We investigate the dynamics of quantum coherence of a system consisting of two interacting atoms coupling with a common cavity which is filled with a nonlinear Kerr-like medium, in the presence of intrinsic decoherence. It is shown that the stationary quantum coherence can arise in the system as the time approach to infinite. In particular, the amount of stationary quantum coherence can be enhanced by adjusting the Kerr interaction and dipole-dipole interaction. Furthermore, we also explore the influence of Kerr interaction and dipole-dipole interaction on the transfer of quantum information by a witness of the trace distance and find that the transferred information and stationary quantum information can be controlled by the Kerr interaction and dipole-dipole interaction.

Periodically driven non-Hermitian quantum systems have become the center of interest in recent years due to their rich physical phenomena. In this work, we consider a one-dimensional non-Hermitian lattice model induced by partially asymmetric coupling with time-periodic and spatially periodic modulations upon on-site potentials. Within Floquet theorem, we obtain the Floquet quasienergy spectrum of this one-dimensional non-Hermitian system. We show that the robust zero-energy modes exist in the band gap from the real parts of quasienergy spectrum. Compared with the case of no modulations, two pairs of the conjugate imaginary parts are added, which can be attributed to the combined modulations upon the on-site potentials. With the increase of non-Hermitian degree, the imaginary parts of the spectra are enlarged. We also observe the dynamical characteristics that, for different kinds of tunneling amplitudes between lattices, the amplitude of evolution gradually either decays to zero or eventually stabilizes at one particular value. Our protocol, possible to realize in photonic lattices, may facilitate the engineering of novel Floquet topological phases in non-Hermitian systems.

A scheme is proposed for fast generation of entangled states in directly coupled bimodal-mode cavities based on shortcuts to adiabatic passage. The scheme can be realized by transitionless quantum driving with the help of quantum Zeno dynamics and non-resonant lasers. First, we simplify the system by the quantum Zeno dynamics. Then, under the large detuning condition, we get the effective Hamiltonian which is equivalent to the corresponding counter-diabatic driving Hamiltonian to speed up the evolution process. The effects of decoherence induced by atomic spontaneous emission, leakage of the cavity and operational imperfection are also taken into account. The numerical simulation result shows that this scheme is robust against these factors. During realizing the scheme, the laser pulses are not strongly limited and the auxiliary levels or multi-step operations are not needed. Moreover, for any quantum system whose Hamiltonian is possible to be simplified into the same form in the paper, the corresponding alternative physically feasible Hamiltonian can be built with present method, which provides a scalable way for the preparation of entangled states in theory.

Descrying all aspects of the quantum entanglement of multipartite quantum systems is an essential part when researching the quantum entanglement. Maximally multi-qubit entangled state is one of the research objects. Recently, attracted by a criterion for maximally entangled nine-qubit state and construct a nine-qubit maximally entangled state, we construct a new genuine maximally nine-qubit entangled state via the recurrence relation. Further, nine-qubit entangled state is found which can be seen as a new form maximally nine-qubit entangled state. There are 108 of purity equal to 1/16, 18 of purity equal to 1/8 in observation. We believe the result could provide a new idea for constructing more new maximally multi-qubit states.

Quantum coherence(QC) and quantum Fisher information(QFI) are investigated for the atom in Jaynes-Cummings model coupling with the Ohmic reservoir at zero temperature when the total excitation number N = 1. We discuss in detail the influence of the atom-cavity coupling and the reservoir parameters on QC and QFI. The results show that QC and QFI of the atom can be effectively controlled by the atom-cavity coupling and the reservoir parameters. Namely, the larger atom-cavity coupling and the appropriate reservoir parameters can effectively protect QC and QFI. Moreover, QC can improve QFI. Last, we provide a physical explanation using the decoherence rate.

Quantum adiabatic theorem is one of the most important conclusions in quantum mechanics, and is widely used in quantum theory and quantum information technology. However, since quantum adiabatic process is a very slow process, factors such as quantum environmental noise or decoherence will affect the results of quantum adiabatic calculation. Therefore, the shortcut to adiabaticity (STA) theory came into being. In this paper, we study the population inversion in a two-level quantum system within a given time, we propose a Lewis-Riesenfeld invariants technique to realize population transfer for the system without the rotating-wave approximation (RWA). According to the invariant condition, the system time-dependent invariant expression is obtained. The amplitudes of Rabi frequency and detuning in the system could be easily controlled by adjusting control parameters. For population inversion, we can get Rabi frequency and detuning by determining the parameters in the invariant. We analyze the dynamics of the system through invariant operators, therefore, no additional coupling is required. Thereby the high-fidelity population transfer can be implemented in two-level quantum system by our method, and it works even without RWA.

We study the dissipative evolution of quantum entanglement and Gaussian interference power in the dynamical Casimir radiation generated in a superconducting waveguide. We consider the decoherence in the current experimental studies, which are in the low temperature. We observe that lower temperature, smaller detuning and larger normalized amplitude can not only maintain the non-classical association of the system more effectively, but also increase the utilization of quantum resources. Moreover, most of the damping is placed on the second noise channel, the entanglement and Gaussian interference power maintain longer and better quality, and they are also more sensitive to other environmental parameters. In addition, the Gaussian interference power is always non-zero, which displays its robustness to the thermal noise and the dissipation.

In line with an experimentally feasible protocol was proposed by A. Asadian et al. [ PRL 112, 190402 (2014)], we introduce a pure dephasing model where the interaction of the central qubit with a nano-mechanical resonator is affected by a spin-bath to study the dynamics of resonator-qubit entangled states. We show that how system-bath coupling as well as the coupling among the bath’s spins, initial semi-classical states of the phonon as well as the initial states of the bath, modify the entanglement of the system using measures like concurrence. To gain insight into the effect of these correlations, we study the dynamics of the mentioned setup both with and without initial correlations for arbitrary system-environment coupling strengths. It is also shown that stable entanglement, which is dependent on correlated initial states of the system-bath, their coupling strength, and bath temperature, occurs even in the presence of decoherence.

Based on the idea of transition from classical optics to quantum optics we deduce the natural expressions of optical beam splitter (BS) and 2-cascaded BS operators in coherent state representation and also obtain their normally ordered forms. Moreover, we theoretically prepare some desired quantum entangled states and investigate several carried experiments. Finally, our work shall be focused on the following two aspects: the quantum-optical catalysis of the BS and quantum state truncation of the 2-cascaded BS.

A novel quantum secret sharing (QSS) protocol is suggested by utilizing the evolution law of atom via cavity quantum electrodynamics (QED) in this paper. It employs two-atom product states rather than entangled states as the initial quantum resource, and adopts single-atom measurements rather than two-atom or multiple-atom joint measurements. It needs neither the unitary operations nor the quantum entanglement swapping. It can resist both the outside attack and the participant attack.

In this paper, we investigate Einstein-Podolsky-Rosen steering, Bell non-locality, first-order coherence and concurrence in the spin- $\frac {1}{2}$ Heisenberg XX model. We first quantify these quantum resources in Heisenberg spin chain model. In fact, the spin chain model will be inevitably affected by environmental noise. Then, we find the dynamical behavior, which is a interaction of two qubits and an open environment, can test the properties of quantum resources. And the influences of these parameters are investigated on quantum resources, including the coupling coefficient, temperature, magnetic field strength and the parameters of channel. Furthermore, we will get dynamical behavior of the stable state under the circumstance of BF channel. And the role of spin chains in quantum information processing can be realized. Finally, we explore the stability of coherence, steering and Bell non-locality in AD channel. These explain how to obtain the ideal quantum state by achieving the control through quantum steering and other operations under noisy environment.

Shared quantum entanglements are rare resources and widely used in various quantum information processing. They are thought sometimes to be more important than local operation and classical communication. In this paper a shared mixing entangled state derived from a pair of Bell states due to participants’ qubit confusion is taken as quantum channel and a quantum teleportation scheme is amply put forward. It is shown that, the state can be used to teleport a single-qubit state with success probability 3/4 rather than discarded. More importantly, from it a Bell state can be derived with 1/2 probability so that whether the teleportation is further proceeded or not can be decided in advance. If not, the unknown state to be teleported will not be destroyed due to the measure. The additional costs in contrast to standard single-qubit state teleportation are two control-not gate operations, two single-qubit measures and a classical-bit message consumption. The underlying reason of abstracting a shared entanglement for quantum teleportation is revealed.

Recently, Pan put forward a quantum dialogue (QD) scheme based on entanglement swapping and Hadamard operation via cavity QED (Int J Theor Phys, 58(2019)1017), and claimed that this scheme is secure. This paper first points out that it runs the risk of information leakage, and then suggests an improvement to remedy this security loophole.

In this paper, we discuss four measures for the quantum and classical correlations of two atoms in a system of two entangled atoms interacting with the Polya field state. In five different initial states of the two atoms, we compare and analyze the influence of the atomic and optical field parameters on the time evolution of the quantum correlation and the classical correlation between two entangled atoms in the considered system. The results show that though the atomic state is initially in a separate one, the time evolution of geometrical quantum discord (GQD), concurrence (C), quantum discord (QD) can still exhibit non zero quantum correlation behavior. The results also show that the time evolution of the three measures of quantum correlation has obvious consistency but the time evolution of classical correlation (CC) is different from that of quantum correlation in the mentioned cases. In addition, the two atoms always remain in the maximum entangled state during the evolution as the two atoms are initially in a maximum entangled state $\left |{\varPsi }_{4}\right \rangle $ .

We study the degree to which the coherence of quantum states is affected by noise. We give the definition of the $n$-th decay rate and investigate the coherence of Bell-diagonal states under $n$ iterations of channels. We derive explicit formulas of the $n$-th decay rates based on $l_1$ norm of coherence, relative entropy of coherence and skew information-based coherence. It is found that the larger $n$ is, the faster the $n$-th decay rate decreases as the parameter $p$ of Bell-diagonal states increases. Moreover, for any fixed $n$, with the increase of $p$, Bell-diagonal states can be completely incoherent under generalized amplitude damping (GAD) channels, depolarization (DEP) channels and phase flip (PF) channels, while this is not the case for bit flip (BF) channels and bit-phase flip (BPF) channels. We also investigate the geometry of the relative entropy of coherence and skew information-based coherence of Bell-diagonal states under different channels when the $n$-th decay rate is one, i.e., the coherence is frozen. It is shown that compared with BF and BPF channels, when $n$ is large enough, the coherence of Bell-diagonal states will not be frozen under GAD, DEP and PF channels. For skew information-based coherence, similar properties of coherence freezing are found.

Recently, utilizing three Bell states as quantum channel, Zhou et al. (Int. J. Quantum Inf. 16, 1850042, 2018) presented a novel scheme for bidirectionally teleporting quantum operations. However, their scheme is unsuccessful. To be exact, it actually only realized bidirectional quantum state teleportation other than quantum operation teleportation they claimed. In this paper, we propose an optimized scheme using the same three Bell States. Compared with that of Zhou et al., our scheme can not only realize the real bidirectional quantum operation teleportation, but also be more lower in the terms of complexity of the necessary operations. Additionally, the status of two users in our scheme is equal.

Quantum nonlocality can be shown by measuring a quantum system containing multipartite entangled state. A key to quantum measurement is to find out what kinds of measurement settings are optimal. We design programable quantum circuit to demonstrate quantum nonlocality for multi-qubit systems based on quantum programming. A series of multiple quantum measurements are performed via cycle structure. As a result, we reveal quantum nonlocality of multipartite quantum systems as well as verify optimizing of measurement settings.

In this work, we study the photon blockade effect based on the anisotropic quantum Rabi model with biased term. Different from the standard quantum Rabi model, such generalized quantum Rabi model allows its rotating and counter-rotating terms to have two different coupling constants and has a biased term. The photon blockade effect is discussed for such model in detail. The results show that the biased and anisotropic parameters play different roles in photon blockade effect. The symmetry of the Hamiltonian system is different when we choose different biased parameters. Consequently, the behavior is modified by varying biased parameters. The ${\mathscr{Z}}_{2}$ symmetry is preserved by varying anisotropic parameters, and the photon statistic behavior is similar for different anisotropic parameters.

A novel bidirectional quantum teleportation schema with GHZ states and EPR pairs via entanglement swapping is proposed. Two GHZ states and two pure EPR pairs build the quantum physical system. Within this quantum system, two entangled GHZ states serve for the quantum channel, and via the entanglement swapping the new entanglements are generated from the involved qbuits after the measurements are performed on both sides. CNOT operation, single qubit measurement and the appropriate unitary transformation are executed on each side, the pure EPR states are simultaneously teleported to each other. The presented protocol bears the economical and efficient advantage compared with the conventional protocols.

We study the effects of Hawking radiation and bath temperature on quantum steering and entanglement for a two-mode Gaussian state exposed in the background of a black hole and immersed in the two independent thermal baths. We find that both the effects can destroy the quantum steering and entanglement. Quantum steering always exists sudden death for any Hawking temperature and any bath temperature, but entanglement does not in zero-temperature thermal bath. Both the Hawking radiation and the asymmetry of thermal baths can induce the asymmetry of quantum steering, but the latter effect is much weaker than the former. An unintuitive result is that the observer who stays in the Hawking radiation or in the thermal bath with higher temperature has more stronger steerability than the other one. We also find that Hawking radiation and thermal noise can change the asymptotic behavior of steering and entanglement versus the squeezing parameter.

In this paper, a quantum correlations analytical treatment for a family of two-ququart states are presented. For this purpose, a family of two-ququart quantum states, as well as a set of von Neumann measurements are proposed. A quantum discord analytical treatment is derived for this family of two-ququart states. Finally, the classical mutual information, the entanglement of formation and quantum discord are illustrated in this family of two-ququart quantum states.

We investigate a new superposition of two coherent states via conditional measurement on a Mach-Zehnder interferometer (MZI). The resulted output state is obtained by using the superposition of two opposite coherent states with the arbitrary relative phase factors for the a-mode and vacuum state in the b-mode. It is shown that the angle of the phase shifter between the two arms of the MZI is a very important parameter in this new state.

We address the teleportation of a two-qubit entangled state through quantum channels where successive uses of the channels are correlated, and investigate how memory effect induced by successive uses of the channels influences the entanglement teleportation and fidelity. The analytical expressions of the entanglement teleportation and average fidelity under three different correlated channels are presented. Our results show that, the output entanglement teleportation strongly depends on the source state, the initial entanglement of teleporting state and parameters of noisy channels. However, the average fidelity is only affected by the parameters of the source state and noisy channels.

In the present article, the robustness of entanglement in two qubits maximally entangled mixed states (MEME) have been studied under quantum decoherence channels. Here we consider bit flip, phase flip, bit-phase-flip, amplitude damping, phase damping and depolarization channels. To quantify the entanglement, the concurrence has been used as an entanglement measure. During this study interesting results have been found for sudden death and birth of entanglement under bit flip and bit-phase-flip channels. While amplitude damping channel produces entanglement sudden death and does not allow re-birth of entanglement. On the other hand, two qubits MEMS exhibit the robust character against the phase flip, phase damping and depolarization channels. The elegant behavior of all the quantum channels have been investigated with varying parameter of quantum state MEMS in different cases., Comment: 15 pages, 7 figures

We explore the dynamics of Einstein-Podolsky-Rosen steering (EPR), measured by steering robustness, for two spin-qubits coupled to a general XY spin chain environment. The evolution process is numerically investigated in the vicinity of critical point for the spin environment. The results show an obvious suppression of steering robustness when the environment undergoes a quantum phase transition. The scaling behavior for the dynamics of EPR steering is also revealed and analyzed around the critical point. Furthermore, we find that steering robustness power (i.e. the average value of steering robustness within a certain time) can indicate the quantum criticality of the environment directly.

We analyze quantum statistical properties for a state describing identical multi spin $$ \frac{1}{2} $$ particle with degeneracy taken into account. This state exhibits nonclassical as well as quadrature squeezing.We also display Q function to demonstrate graphically nonclassical features of this state in the phase space.

A hybrid quantum optomechanical system is an interface made from coupling between photons, excitons and mechanical oscillations. We use the quantum Langevin approach to study a hybrid optomechanical system which contains a single undoped semiconductor quantum well placed inside a cavity as well as one mirror of the optical resonator linear coupled to the cavity fields. A decorrelation method is employed to get a closed set of coupled equations. Furthermore, we have used these solutions to discuss squeezing dynamics for the coupled mode quadratures of the cavity field and the semiconductor quantum well exciton. We have illustrated that squeezing dynamics can be controlled by appropriate choice of physical parameters present in our hybrid optomechanical system.

The adiabatic theorem, an important theory in quantum mechanics, tells that a quantum system subjected to gradually changing external conditions remains to the same instantaneous eigenstate of its Hamiltonian as it initially in. In this paper, we study the quench evolution that is another extreme circumstance where the external conditions vary rapidly such that the quantum system can not follow the change and remains in its initial state (or wavefunction). We examine the matter-wave pressure and derive the requirement for such an evolution. The study is conducted by considering a quantum particle in an infinitely deep potential, the potential width Q is assumed to be change rapidly. We show that the total energy of the quantum subsystem decreases as Q increases, and this rapidly change exerts a force on the wall which plays the role of boundary of the potential. For Q Q0, the force is positive. The condition for the quenching evolution evolution is given via a spin- $$ \frac{1}{2} $$ in a rotating magnetic field.

The methods of quickly achieving the adiabatic effect through a non-adiabatic process has recently drawn widely attention both in quantum and classical regime. In this work ,we study the classical adiabatic shortcut for two- and three-Level atoms by transforming the quantum version into classical one via quantum-classical corresponding theory. The results shows that, the additional couplings between the oscillators can be used to speed up the adiabatic evolution of coupled oscillators. Furthermore, we find that the quantum-classical correspondence theory still holds for the couter-adiabatic driving Hamiltonian for the TQD. This means that, we can obtain the counter-adiabatic driving Hamiltonian for a classical system by averaging over its quantum correspondence in a quantum system. This provides a feasible way to study the classical adiabatic shortcut and the simulation for the quantum adiabatic shortcut in a classical system.

Following the lines of the recent papers (Daneshmand and Tavassoly, Int. J. Theor. Phys. 56, 1218 (2017)), we study quantum mechanical treatments of an interaction between a two-level atom with a single-mode field in the two-photon Jaynes-Cummings model, where the Hamiltonian of the field is considered to be the quantized Caldirola-Kanai (CK) Hamiltonian. As a result, we would expect that the quantum dynamics of the two-photon JCM in terms of the CK Hamiltonian is qualitatively different from that of the usual one-photon case. We analytically calculate the explicit form of the atom-field entangled state and numerically evaluate the dynamics of its physical properties. The degree of entanglement, atomic population as well as sub-Poissonian statistics and quadrature squeezing of the field are analyzed. We adjust the latter evolved parameters by appropriately tuning the damping parameter within the CK Hamiltonian and detuning factor. Finally, we report a field detuning asymmetry in the collective statistical behavior.

The purpose of this paper is to discuss the Hawking radiation of vector particles from a quantum correction black hole by the mean of quantum tunneling. In order to achieve this purpose, based on the Proca field equation and WKB approximation, the quantum tunneling method is used to calculate the tunneling rate and Hawking temperature of the black hole. According to the analysis of the consequences, we find that the tunneling rate and Hawking temperature are related to the quantum parameter besides the horizon radius and mass of the black hole. Furthermore, when the results are compared with those of scalar particles and fermions of the black hole, no difference is found. Therefore, the tunneling rate and Hawing temperature of the black hole do not change with the type of radiation particles.

Quantum measurement and quantum operation theory is developed here by taking the relational properties among quantum systems, instead of the independent properties of a quantum system, as the most fundamental elements. By studying how the relational probability amplitude matrix is transformed and how mutual information is exchanged during measurement, we derive the formulation that is mathematically equivalent to the traditional quantum measurement theory. More importantly, the formulation results in significant conceptual consequences. We show that for a given quantum system, it is possible to describe its time evolution without explicitly calling out a reference system. However, description of a quantum measurement must be explicitly relative. Traditional quantum mechanics assumes a super observer who can instantaneously know the measurement results from any location. For a composite system consists space-like separated subsystems, the assumption of super observer must be abandoned and the relational formulation of quantum measurement becomes necessary. This is confirmed in the resolution of EPR paradox. Information exchange is relative to a local observer in quantum mechanics. Different local observers can achieve consistent descriptions of a quantum system if they are synchronized on the information regarding outcomes from any measurement performed on the system. It is suggested that the synchronization of measurement results from different observers is a necessary step when combining quantum mechanics with the relativity theory.