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We investigate the quantum thermodynamic cycle of a quantum heat engine carrying out an Otto thermodynamic cycle. We use the thermal properties of a moving heat bath with relativistic velocity with respect to the cold bath. As a working medium, we use a two-level system and a harmonic oscillator that interact with a moving heat bath and a static cold bath. In the current work, the quantum heat engine is studied in the high and low temperatures regime. Using quantum thermodynamics and the theory of open quantum system we obtain the total produced work, the efficiency and the efficiency at maximum power. The maximum efficiency of the Otto quantum heat engine depends only on the ratio of the minimum and maximum energy gaps. On the contrary, the efficiency at maximum power and the extracted work decreases with the velocity since the motion of the heat bath has an energy cost for the quantum heat engine. Furthermore, the efficiency at maximum power depends on the nature of the working medium., 16 pages, 4 figures

We study the QSLT of the two-level system coupling to a single mode cavity which is driven by a laser field under the feedback control, and focus on the effect of the Rabi frequency and two types of the feedback on the QSLT. The results show that the QSLT is always less than the driving time, that is, the evolution speed of the two-level system can be accelerated. Whatever types of feedback we use, the QSLT varies with the initial time parameter, both the feedback and the classical field can change the acceleration in the evolution process.

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.

In classical information processing, the windowed Fourier transform (WFT), or short-time Fourier transform, which is a variant of the Fourier transform by dividing a longer time signal into shorter segments of equal length and then computing the Fourier transform separately on each shorter segment, is proposed to provide a method of signal processing. Up to now the discrete Fourier transform has been successfully applied to the field of quantum information, but the related short-time discrete Fourier transform of this field has not been developed accordingly. To address this problem, we first introduce the concept of quantum window state, and further prove that the quantum Fourier transform of a quantum window state is also a quantum window state. Based on the definition of the quantum window state the local information of a quantum signal is extracted and the corresponding quantum circuits are also given. And then, by applying the quantum Fourier transform to the windowed quantum superposition states, we propose a novel concept called quantum windowed Fourier transform (QWFT). Finally, an application of quantum signal processing is given where QWFT is employed.

We consider a parametric oscillation driven by coherent light beams and coupled to a two-mode thermal reservoir. Applying the solutions of the quantum Langevin equations, we investigate the effect of decoherence and the driving coherent light beams on the squeezing and entanglement as well as statistical properties of the two-mode cavity radiation. We show that the two-mode thermal noise and the driving coherent light beams lead to an increase in the intensity of the cavity radiation. However, the driving coherent light beams do not have any effect on the squeezing and entanglement properties of the two-mode cavity radiation while the two-mode thermal noise leads to a decrease in the degree of squeezing and entanglement of the two-mode cavity radiation.

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.

Using the thermal-entangled state representations, we obtain the analytical evolution of quantum states simultaneously undergoing two kinds of quantum noises that can be represented as the infinitive Kraus operator-sum representation. We also prove the normalization and trace preservation of Kraus operators. Besides, we obtain the evolutions of Wigner distribution and photon number distribution of any quantum state when simultaneously passing through two kinds of quantum noises.

Quantum logic gates are the foundation of circuit-based quantum computation and quantum simulation. Multi-qubit quantum controlled gates are of vital importance when large-scale quantum circuits are concerned. Here, assisted by diamond nitrogen-vacancy (NV) centers inside single-sided optical cavities, we first introduce the single-photon quantum routing operation, with which a single-photon polarization qubit can be coherently routed to the superposition of two spatial modes according to the state of the other polarization qubit. On this basis, we propose two schemes for the implementation of universal three-qubit quantum Fredkin- and Toffoli-gate operations on single-photon polarization qubits. Moreover, we show that a general multi-qubit controlled-unitary gate can be realized using the same strategy. Compared to other NV-cavity-based schemes, our schemes utilize photonic polarization, spatial, and temporal degrees of freedom (DOFs) simultaneously, so that the quantum circuits are simplified and the required quantum resources are reduced, making our schemes more resource-efficient and highly scalable. Our calculations show that the schemes can posses near-deterministic efficiency and near-unity fidelity with current or near-future techniques, which guarantees the experimental feasibility. Our schemes can therefore provide a new recipe for the construction of multi-qubit quantum gates and for efficient processing of multi-photon states.

We explore quantum multi-parameter estimation, based on quantum Fisher information matrix (QFIM), in an extended anisotropic XY spin chain associated with non-trivial topological characterization driven by varying system parameters (i.e., magnetic field λ, the anisotropic of the nearest-neighbor interaction γ, the next-nearest-neighbor interaction α and its anisotropy δ). The results show that QFIM can provide us a useful tool to detect the topological critical points in this model. Furthermore, we find that the behavior of QFIM associated with variance of estimators are driving parameters dependent at different topological quantum phase transition points. Meanwhile, the choice of estimators $\hat {\theta }$ also take a prominent role on the behavior of QFIM.

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.

The analog multicolor optomechanically induced transparency (OMIT) of distant optomechanical system is studied. The two charged mechanical oscillators couple to each other via Coulomb interaction, and the atomic ensemble is introduced into the hybrid system. We focus on the width of OMIT windows which is manipulated by some interference effects of the system components. The research shows that five transparency windows can be observed from the output field at the probe frequency. In the absence of some internal interactions, the number of transparent windows will reduce. Furthermore, the width and the number of the transparent windows are affected by the coupling strength between the optical mode and the mechanical mode, between the optical mode and atoms and the Rabi frequency, between the two optical modes, as well as the Coulomb coupling between the two charged oscillators. It is feasible for our approach to manipulate multiple optomechanically induced transparency, which provides potential applications in quantum information processing and quantum net works.

In this paper, we study cyclic codes over a finite non-chain ring $\mathbb {F}_{p^{m}}+v\mathbb {F}_{p^{m}}$ with v2 = 1 and find new and better quantum error-correcting codes than previously known quantum error correcting codes over $\mathbb {F}_{p^{m}}$ . Therewith, we characterize the LCD codes and obtain many new LCD codes. Also, we prove that the Gray map of an LCD code of length n over $\mathbb {F}_{p^{m}}+v\mathbb {F}_{p^{m}}$ is an LCD code of length 2n over $\mathbb {F}_{p^{m}}$ .

Quantum enhancement of the optical behavior for V −type open atomic system is examined analytically. With consideration of the system which contain N number of atoms, it is derived that the evolution of the atomic variable evolution with respect to time. At steady state, the optical properties of the system have been analyzed. The phase between the upper doublet levels is influencing the optical parameters change in the system. It is observed that for small values of the phase between the upper doublet energy states, the better refractive index of the atomic medium. The refractive index gets the peak value near to the resonance frequency of the probe field. The properties of the re-emitted light from ensemble of three-level atoms have been analyzed in details. In this regard, it is observed that the height of the power spectrum increased while the number of atoms are large in the sample.

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.

With entanglement-assisted (EA) formalism, arbitrary classical linear codes are allowed to transform into EAQECCs by using pre-shared entanglement between the sender and the receiver. In this paper, based on classical cyclic MDS codes by exploiting pre-shared maximally entangled states, we construct two families of $q$-ary entanglement-assisted quantum MDS codes $[[\frac{q^{2}+1}{a},\frac{q^{2}+1}{a}-2(d-1)+c,d;c]]$, where q is a prime power in the form of $am+l$, and $a=(l^2+1)$ or $a=\frac{(l^2+1)}{5}$. We show that all of $q$-ary EAQMDS have minimum distance upper limit much larger than the known quantum MDS (QMDS) codes of the same length. Most of these $q$-ary EAQMDS codes are new in the sense that their parameters are not covered by the codes available in the literature., arXiv admin note: substantial text overlap with arXiv:1803.04168, arXiv:1912.12031

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.

Quantum degenerate systems can be simulated by the classical resonant oscillators in the means of quantum-classical mapping theory. In this work, we show the classical version of shortcuts to adiabaticity-transitionless quantum driving (TQD) for the non-Abelian quantum systems by averaging the quantum version. The non-Abelian geometric angle corresponding to the quantum Wilczek-Zee phase is given and the non-Abelian angle gauge potential is just the opposite of the third term of TQD Hamiltonian or the averaging of Wilczek-Zee gauge potential. An example of Hamiltonian with two degenerate subspaces is employed to illustrate the classical non-Abelian dynamics, geometric angle and shortcuts to adiabaticity. This provides a promising platform to simulate the quantum shortcut or for quantum computation and quantum information processing.

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.

In this paper, a linear generalized uncertainty principle (GUP), which suggests a minimum measurable length and a maximal measurable momentum, is used in analyzing COW experiment and Einstein-Bohr’s a photon box experiment. Based in these experiments a modified Schwarzschild metric was obtained in order to calculate a quantum corrections in Schwarzschild black hole thermodynamics and tunneling probability. It was found that GUP placed restrictions on the minimum mass, size and temperature of the black hole, indicating that there was a black hole remnant after the completion of the evaporation process. The resulting values of minimum mass and size of the black hole are identical to that values predicted by quadratic GUP, which points out that the two models are equivalence in Planck scale measurements.

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.

We research the strong gravitational lensing for the quantum-modified Schwarzschild black hole which is derived from quantum Raychaudhuri equation. With the increase of quantum Raychaudhuri equation parameter η, we find that the distance between the black hole and the light passing by it becomes smaller; the deflection angle gets larger; the magnification of relativistic images is more similar; all of the relativistic images move towards the black hole while the images are farther to each other. These results, as we expect, will degenerate to the case of Schwarzschild black hole when $\eta \rightarrow 0$ .

The construction of maximum distance separable (MDS) linear complementary dual (LCD) codes and entanglement-assisted quantum MDS (EAQMDS) codes have been of a great interest. In this paper, for arbitrary prime power q, we construct two new families of MDS Hermitian LCD codes of length $n=\frac {{{q^{2}}+1}}{\lambda }$ and $n=\frac {q^{2}-1}{r},$ where rq + 1. By applying the obtained MDS Hermitian LCD codes to the EAQMDS codes, we derive new maximal entanglement EAQMDS codes of parameters ${\left [ \kern -0.30em\left [ {\frac {{{q^{2}}+1}}{\lambda },\frac {{{q^{2}}+1}}{\lambda }-l+1,l;l-1}\right ] \kern -0.30em\right ]_{q}}$ where $2\leq l\leq \left \lfloor \frac {{{q^{2}}+1+2\lambda }}{2\lambda }\right \rfloor $ and ${\left [ \kern -0.30em\left [ {\frac {{{q^{2}-}1}}{r},\frac {{{q^{2}-}1}}{r} -\gamma ,\gamma +1;\gamma }\right ] \kern -0.30em\right ]_{q}}$ where $1\leq \gamma \leq \frac {{{q^{2}}-1}}{2r}.$

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.

Photonic hyperentanglement, which involves photons simultaneously entangled in more than one degree of freedom (DOF), has many important applications in quantum information processing, especially in high-capacity quantum communications. Interestingly, single-photon qubits encoded in the time-bin DOF are robust for long-distance transmissions in noisy channels. In this paper, we present a hyperentangled-Bell-state generation (HBSG) scheme for preparing two-photon six-qubit states which are simultaneously entangled in the polarization, spatial-mode, and time-bin DOFs. Compared with previous HBSG schemes, we construct an error-detected circuit unit with a quantum-dot (QD) spin in a double-sided optical microcavity, with which errors due to imperfect interactions between photons and QD systems can be easily detected, so that the error-detected circuit unit can relax the experimental requirement and improve the fidelity of our scheme largely. Meanwhile, our scheme is used to prepare two-photon hyperentangled states in polarization-spatial-time three DOFs, which is significant for faithful entanglement distribution and quantum repeater. These features make our scheme more feasible and useful in high-capacity and long-distance quantum communications with hyperentanglement.

The conformal cyclic cosmological evolution of the universe is discussed with the principles of loop quantum gravity. The application of quantum mechanical aspects enables connecting surface between two cyclic aeons. From existing models entropy of conformal evolution is found to be modified in the light of this discussion. Infinite volume problem in conformal cyclic cosmology model is resolved with these loop quantum gravitational solutions. Various bouncing scale factors are compared. Conformal cyclic cosmological evolution does have a connection with the loop quantum cosmological scenario with this idea bridged. This work briefs the possible initial and final stages of the universe from the CCC and LQG scenario. In the connecting point between two aeons, the existence of curvature duality is also obtained and presented.

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.

The purpose of this paper is to develop a (N − k) threshold quantum secret sharing (QSS) scheme by using entangled multi-qudit states shared between N qudits such that (k ≤ N − k). We introduce first multi-qudit separable states of a Hilbert space associated with a disconnected multi-qudit system. The entangled multi-qudit states are obtained from disconnected states by means of a unitary interaction operator governing the evolution of the multi-qudit system, where the pairwise interaction establishes links between qudits. The generated entangled states are chosen to be maximally entangled with respect to a specific bi-partition ( $A_{2} \bigcup A_{1} $ ) with k = |A2|≤|A1| = (N − k) of the whole system such that the von Neumann entropy $S(\rho _{A_{2}})$ is maximal. The maximally entanglement property with respect to the splitting ( $A_{2} \bigcup A_{1} $ ) of this N-qudit entangled states will be used by a dealer (D) to share an encoded quantum secret with (N − 1) other players, such that at least the (N − k) specified players belonging to A1 have to cooperate jointly to get the complete information about the secret.

In this paper, we propose that the behavior of quantum particles assuming discreteness of the spacetime at very low scale is similar to the behavior of Anyons.

In this paper, we have presented an analytical and numerical study of a matter wave packet propagation in a disordered optical potential. We have used the self-consistent Born approximation which is well supported in weak disorder to calculate the real part of the self- energy RΣ(e, p). The difference of 0.1 which appears between the analytical and numerical calculation is very acceptable. The varying of disorder amplitude change the position of the critical energy of the transition which it can be larger or smaller than correlation energy. This analysis gives new insight into numerical result. We propose to analyze the behavior of the energy distribution with this quantum corrected diffusion factor, which is a very important parameter for the mobility edge prediction. Our results open new interesting studies and provide good reference data for future research such as the behavior of the mobility edge in fractal systems and the evolution of the density of condensates in time and space.

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.

Time-series analysis and network analysis are now used extensively in diverse areas of science. In this paper, we applythese techniques to quantum dynamics in an optomechanical system: specifically, the long-time dynamics of the mean photon number in an archetypal tripartite quantum system comprising a single-mode radiation field interacting with a two-level atom and an oscillating membrane. We also investigate a classical system of interacting Duffing oscillators which effectively mimics several of the features of tripartite quantum-optical systems. In both cases, we examine the manner in which the maximal Lyapunov exponent obtained from a detailed time-series analysis varies with changes in an appropriate tunable parameter of the system. Network analysis is employed in both the quantum and classical models to identify suitable network quantifiers which will reflect these variations with the system parameter. This is a novel approach towards (i) examining how a considerably smaller data set (the network) obtained from a long time series of dynamical variables captures important aspects of the underlying dynamics, and (ii) identifying the differences between classical and quantum dynamics., 8 pages, 8 plots

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 this study, we have generalized the fractional action integral by using the Saigo-Maeda fractional operators defined in terms of the Appell hypergeometric function of two variables , F3(a, a′, β, β′; γ; z, ζ) with complex parameters. We have derived the associated Euler-Lagrange equation and we have studied the harmonic oscillator problem. We have proved that a PT -symmetric quantum-mechanical Hamiltonian characterized by real and discrete spectra is obtained although the system is characterized by complex trajectories. The associated thermodynamical properties were discussed and it was revealed the entropy of the quantum system decreases with time toward an asymptotically positive value similar to what is observed in quantum Maxwell demon.

In this work, we study the adiabatic phases and shortcut for a pseudo-Hermitian interacting spin-1/2 composite system in which one system is driven by a non-Hermitian magnetic field. The biorthonormal eigenbasis and the condition for real eigenvalues have been derived and discussed. By studying the Berry phases and the transitionless quantum driving (TQD) Hamiltonian, the roles of correlation between the subsystems and the non-Hermicity are discussed. The non-Hermitian dynamics and the Berry phases of the subsystem, as well as their influences on the TQD Hamiltonian are studied in both no correlation and large correlation cases. These results mean that we can modify the correlation between the subsystems to control the adiabatic shortcuts of the subsystems. These schemes can provide a feasible way for studying the adiabatic shortcuts of the composite system and the non-Hermitian system.

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.

In the thermodynamic evolution of black holes, the generalized uncertainty principle and quantum tunneling effect prevent the complete evaporation of black holes and produce remnants, and thermodynamic phase transition occurs during evaporation. Based on the generalized uncertainty principle and the method of quantum tunneling, we study the phase transition of the quantum–corrected black hole. Using the modified Hamiltonian–Jacobi equation to analyze the corrected thermodynamic quantity, we find that the thermodynamic phase transition of the black hole is not only depending on the nature of the black hole itself, it also depends on quantum parameter ξ, generalized uncertainty parameter β and parameter λ.