Separability and Entanglement of the Qudit X-State with j = 3/2

We study the qudit state with spin j = 3/2 and the density matrix of the form corresponding to the X state of two qubits and consider the entanglement and separability properties. We use the qubit portrait of qudit states to obtain the entropic inequalities for the entangled state of a single qudit. We present the tomographic-probability representation of the qudit X-state and obtain the Shannon and q entropic characteristics in explicit forms.     

Deformed Subadditivity Condition for Qudit States and Hybrid Positive Maps

We extend the subadditivity condition for q-deformed entropy of a bipartite quantum system to the case of an arbitrary quantum system including the single qudit state. We present the subadditivity condition for the density matrix of the single qutrit state in an explicit form. We obtain the inequality for the purity parameters of a bipartite quantum system and its subsystems. We propose a positive map construction using the fiducial density matrix.     

Subadditivity Condition for Spin Tomograms and Density Matrices of Arbitrary Composite and Noncomposite Qudit Systems

We obtain a new quantum entropic inequality for the states of a system of n ≥ 1 qudits. The inequality has the form of the quantum subadditivity condition of a bipartite qudit system and coincides with the subadditivity condition for the system of two qudits. We formulate a general statement on the existence of the subadditivity condition for an arbitrary probability distribution and an arbitrary qudit-system tomogram. We discuss the nonlinear quantum channels creating the entangled states from separable states.     

Subadditivity and Strong Subadditivity Conditions for the Density Matrix of the Five-Level Atom

We obtain new quantum inequalities for von Neumann entropy of the five-level atom, which are analogs of the subadditivity condition known for bipartite quantum systems and the strong subadditivity condition known for tripartite quantum systems. We discuss the possibility to check the inequalities for the single qudit with j = 2, which can be realized as a five-level atom in the experiments with superconducting circuits. We present the strong subadditivity conditions for the finite-level atomic populations.     

Tomographic Discord and Quantum Correlations in a System of Qubits

We introduce the difference in quantum mutual information for a bipartite system of qubits and the minimum taken with respect to the local unitary transformation group as a characteristic of quantum correlations of the system tomographic mutual information. We study in detail the example of two qubits and the X state of two qubits.     

Surface Majorana flat bands in j=3/2 superconductors with singlet-quintet mixing

Recent experiments [Science Advances 4 eaao4513(2018)] have revealed the evidence of nodal-line superconductivity in half-Heusler superconductors, e.g., YPt Bi. Theories have suggested the topological nature of such nodal-line superconductivity and proposed the existence of surface Majorana flat bands on the(111) surface of half-Heusler superconductors.Due to the divergent density of states of the surface Majorana flat bands, the surface order parameter and the surface impurity play essential roles in determining the surface properties. We study the effect of the surface order parameter and the surface impurity on the surface Majorana flat bands of half-Heusler superconductors based on the Luttinger model. To be specific, we consider the topological nodal-line superconducting phase induced by the singlet-quintet pairing mixing, classify all the possible translationally invariant order parameters for the surface states according to irreducible representations of C_(3v)point group, and demonstrate that any energetically favorable order parameter needs to break the time-reversal symmetry. We further discuss the energy splitting in the energy spectrum of surface Majorana flat bands induced by different order parameters and non-magnetic or magnetic impurities. We propose that the splitting in the energy spectrum can serve as the fingerprint of the pairing symmetry and mean-field order parameters. Our theoretical prediction can be examined in the future scanning tunneling microscopy experiments.     

Quantum Coherence and Degree of Mixedness for a System of Two Superconducting Qubits Under Decoherence Conditions

Journal of Russian Laser Research - In this work, we study quantum coherence, the degree of mixedness, and total quantum correlation in two interacting superconducting charge qubits (SCQs) in both...     

Intermediate electronic relaxation betweenS=3/2 andS=1/2 states in Fe(J-mph)NO with a jäger-type ligand J-mph

The incomplete spin transition between the low-spin (LS) (S=1/2) and the intermediate-spin (IS) (S=3/2) states in the iron (III) complex Fe(J-mph)NO (mph=4-methyl-o-phenylene), centered atT _c≈212 K, has been studied with⁵⁷Fe Mössbauer spectroscopy and magnetic susceptibility measurements between 80 K and 320 K. The lineshape of the Mössbauer spectra is well reproduced by a two state stochastic relaxation model resulting in values of about 2·10⁶ s^?1 to 7·10⁶ s^?1 for the IS→LS transition rate constantk _IL. The kinetics of this spin transition can be described by an Arrhenius equation yielding activation energiesE _IL=1.1 (2) kJ/mol andE _LI=6.1 (2) kJ/mol for the IS→LS and LS→IS conversion, respectively.     

Concurrence and Negativity as a Family of Two Measures Elaborated for Pure Qudit States

We investigate entangled states of an atomic trapped ion interacting with two phonons in the Λ configuration forming a twelve-dimensional Hilbert space. We study two elaborated measures, namely, the concurrence C and negativity N, which are important in current theoretical studies. Therefore, we work with the three-dimensional reduced density matrix in calculating the measures elaborated for pure qudit states in the ionic–phononic system. To demonstrate the benefits of the family of the two measures elaborated, we perform the calculations for different values of the Lamb–Dicke (LD) parameter η = 0.01, 0.3, and 0.5. Finally, we show that the pure qudit states under study are maximum entangled states.     

Entangled Subspaces for Two Coupled Qubits in a Normal Environment

By investigating the effect of environmental perturbations on two initially coupled qubits, we find that the interactions between the qubits and between the qubits and the environment are not only the source of decoherence, but also the power of avoiding disentanglement. It is shown that there are the entangled subspaces for four kinds of different coupling ways between the qubits, in which the qubits preserve entanglement all the time. Thus, any new coherent source does not be introduced to preserve entanglement in the entangled subspaces.     

Entanglement Generation for Two Coupled Multi-excitation Fields Interacting with Qubits

We study the entanglement dynamics for two coupled multi-excitation cavity fields, each independently interacting with a two-level atom. We find that even when the atom-field system is initially not entangled, the fields can become heavily entangled through postselecting of the atomic state. The field entanglement entropy is dependent on the total excitation number but independent of the coherent photon hopping strength.     

Quantum Discord Behavior for Two Qubits Heisenberg XYZ Chain with Inhomogeneous Magnetic Field

We report the quantum correlation behavior (quantum discord (QD)) of a two-qubit anisotropic Heisenberg XYZ chain under an inhomogeneous magnetic field. It is shown that in the lower region of b QD can be enhanced evidently through increasing anisotropic parameter γ, while the effects of γ are disappear when b is strong enough. The role of J _z is nearly opposite to γ, there is a critical value of b _c , with b>b _c QD is improved with decreasing interaction J _z , while the value of QD is nearly invariable whatever changing J _z when b<b _c . In addition, one can get non-zero QD by properly tuning J _z and γ even at a higher temperature. When inhomogeneity is increased to b _c , the QD can exhibit a regrowth procession, and the regrowth value of QD can be larger than that of before dropping in the region of weak J _z . We also obtain the ground state QD properties. These investigations can imply us more control parameters on quantum correlation in solid state systems.     

Helicity Amplitudes for Photoproduction of Baryons with J = 1/2 and JP = 3/2+

We derive the separate helicity amplitudes using the partial wave analysis in the process of pseudo-scalar meson photoproduction. For J^P = 3/2⁺, we find the amplitude is model independent. According to parity conservation, the general amplitude in the case of J^P = 1/2^- is obtained. We prove this general amplitude corresponds to the situation of λ= -1 when adopting the circular polarization. Finally, the formulas of scattering amplitudes involving the meson photoproduction with J^P = 3/2⁺ are obtained from the chiral quark model.     

Helicity Amplitudes for Photoproduction of Baryons with J=1/2 and J~P=3/2~+

We derive the separate helicity amplitudes using the partial wave analysis in the process of pseudo-scalar meson photoproduction.For J~P= 3/2~+,we find the amplitude is model independent.According to parity conservation,the general amplitude in the case of J~P=1/2 is obtained.We prove this general amplitude corresponds to the situation of λ=-1 when adopting the circular polarization.Finally,the formulas of scattering amplitudes involving the meson photoproduction with J~P= 3/2~+ are obtained from the chiral quark model.     

The Transfer and Monogamy of Quantum Correlations for Two Qubits

In this paper the entanglement and the quantum discord (QD) dynamics of two cavities interacting with a common independent reservoir are investigated. Remarkably, it has been proved that the entanglement between two cavities can be transferred to one of the cavities and the reservoir with time evolution. Compared with the dynamics of entanglement, the QD has the similar behavior. It is found that the cavity damping rate can stabilize the entanglement and quantum discord between the cavity and reservoir. We also explore the monogamy of the entanglement and the QD during the interaction of quantum system.     

Entanglement Dynamics of Two Spin Qubits in a Spin Environment with Nonuniform Coupling

We investigate the entanglement dynamics of a two-spin-qubit system coupled to a spin environment with nonuniform coupling through using the time-dependent density-matrix renormalization group method. We show that the entanglement generation and decay depend on the number of environment spins, the coupling strength between the central spin system and the environment, and the initial state of the central spin system.     

Steady Quantum Discord Behavior for Two Qubits Heisenberg XYZ Chain with Intrinsic Decoherence

By taking into account the intrinsic decoherence and the nonuniform magnetic field, quantum discord (QD) and steady quantum discord (SQD) behavior of a two-qubit anisotropic Heisenberg XYZ chain with different initial states are investigated. We find that properly tuning the external and self parameters not only can improve the quantum correlation and steady quantum correlation but also can weaken the effects of decoherence such as increasing anisotropic parameter Δ, decreasing B or b. When t is infinity, the SQD value and the physical about the SQD phenomenon are studied in detail, the SQD value is strongly dependent on the external and self parameters, which is increased evidently by increasing anisotropic parameter and decreasing nonuniform field. Through analyzing the physical about SQD phenomenon, the conditions about the existence of SQD phenomenon are analyzed with different initial states. These investigations can imply us more control parameters on quantum correlation and steady quantum correlation in solid state systems.     

Dynamics of Spin I=3/2 under Spin-Locking Conditions in an Ordered Environment

We have derived approximate analytic solutions to the master equation describing the evolution of the spin I=3/2 density operator in the presence of a radio-frequency (RF) field and both static and fluctuating quadrupolar interactions. Spectra resulting from Fourier transformation of the evolutions of the on-resonance spin-locked magnetization into the various coherences display two satellite pairs and, in some cases, a central line. The central line is generally trimodal, consisting of a narrow component related to a slowly relaxing mode and two broad components pertaining to two faster relaxing modes. The rates of the fast modes are sensitive to slow molecular motion. Neither the amplitude nor the width of the narrow component is affected by the magnitude of the static coupling, whereas the corresponding features of the broad components depend in a rather complicated manner on the spin-lock field strength and static quadrupolar interaction. Under certain experimental conditions, the dependencies of the amplitudes on the dynamics are seen to vanish and the relaxation rates reduce to relatively simple expressions. One of the promising emerging features is the fact that the evolutions into the selectively detected quadrupolar spin polarization order and the rank-two double-quantum coherence do not exhibit a slowly relaxing mode and are particularly sensitive to slow molecular motion. Furthermore, these coherences can only be excited in the presence of a static coupling and this makes it possible to discern nuclei in anisotropic from those in isotropic environment. The feasibility of the spin-lock pulse sequences with limited RF power and a nonvanishing average electric field gradient has been demonstrated through experiments on sodium in a dense lyotropic DNA liquid crystal.