Presence Of Intrinsic Decoherence Research Articles

Effects of Dzyaloshinskii-Moriya interaction and intrinsic decoherence on quantum dense coding via a two-qubit Heisenberg spin system

By solving the Milburn equation, we investigate the properties of optimal channel capacity for the quantum dense coding via a two-qubit Heisenberg spin system with Dzyaloshinskii-Moriya (DM) interaction in the presence of intrinsic decoherence. The influences of different DM interactions, different initial states, anisotropic coupling parameters, and intrinsic decoherence on optimal coding capacity are analyzed in detail. It is found that the initial state of the system affects optimal coding capacity greatly, whose dependent parameters are not identical for different types of initial states. When the system is initially in the form of the nonmaximally entangled state cft| {01} ightangle + dft| {10} ightangle , a weak z-component DM interaction can enhance the value of optimal coding capacity as compared with the value without DM interaction, and the phase decoherence effect can suppress the oscillation of optimal coding capacity and make the capacity decrease to a stable value for the long-time evolution. It is also found that under the influence of intrinsic decoherence, the optimal transmission capacity of dense coding can keep an ideal maximal value of 2 by choosing the proper initial maximally entangled state. Moreover, no matter from which direction the DM interaction is introduced, the optimal coding capacity via the two-qubit Heisenberg spin system is always larger than the transmission capacity of any classical communication.

Properties and coherence-controlling of entanglement of a two-qubit Heisenberg XY chain with intrinsic decoherence

By solving the Milburn equation, we investigate the thermal entanglement properties of a two-qubit Heisenberg XY chain in the presence of intrinsic decoherence. The controls of nonuniform magnetic field, the initial state of two qubits, the relative phases and the amplitudes of the polarized qubits on thermal entanglement are studied. The results show that for a particular initial state, the thermal entanglement can be increased by the external magnetic field. The time behavior of the entanglement exhibits a strong dependence on the initial state of two qubits, and it can be manipulated by changing the relative phase and the amplitudes of the polarized qubits. It is also notable that stable entanglement, which is dependent on initial state of the qubit, occurs even in the presence of decoherence. The magnetic field may have a constructive effect on the stable entanglement for a certain initial state, and the Bell-diagonal state turns out to be a dark state of the system in the absence of the magnetic field.

Analysis of mixed state entanglement with intrinsic decoherence

We analyze different entanglement measures for a mixed state two-level system in the presence of intrinsic decoherence. The information about entanglement is obtained by comparing the results for the atomic Wehrl entropy and negativity with the analytical results for a simple case. For the strong decoherence case we find that a similar and long-lived maximum Wehrl entropy and negativity between atom and field are shown. The results highlight the important roles played by both the decoherence parameter and the initial state setting in determining the evolution of the atomic Wehrl entropy and negativity.

Influence of dephasing on the entanglement teleportation via a two-qubit Heisenberg XYZ system

We study the entanglement dynamics of an anisotropic two-qubit Heisenberg XYZ system in the presence of intrinsic decoherence. The usefulness of such a system for performance of the quantum teleportation protocol $\mathcal{T}_0$ and entanglement teleportation protocol $\mathcal{T}_1$ is also investigated. The results depend on the initial conditions and the parameters of the system. The roles of system parameters such as the inhomogeneity of the magnetic field b and the spin-orbit interaction parameter D, in entanglement dynamics and fidelity of teleportation, are studied for both product and maximally entangled initial states of the resource. We show that for the product and maximally entangled initial states, increasing D amplifies the effects of dephasing and hence decreases the asymptotic entanglement and fidelity of the teleportation. For a product initial state and specific interval of the magnetic field B, the asymptotic entanglement and hence the fidelity of teleportation can be improved by increasing B. The XY and XYZ Heisenberg systems provide a minimal resource entanglement, required for realizing efficient teleportation. Also, in the absence of the magnetic field, the degree of entanglement is preserved for the maximally entangled initial states $\left| {\psi \left. {\left( 0 \right)} \right\rangle = \frac{1} {{\sqrt 2 }}\left( {\left| {\left. {00} \right\rangle \pm } \right|\left. {11} \right\rangle } \right)} \right.$ . The same is true for the maximally entangled initial states $\left| {\psi \left. {\left( 0 \right)} \right\rangle = \frac{1} {{\sqrt 2 }}\left( {\left| {\left. {01} \right\rangle \pm } \right|\left. {10} \right\rangle } \right)} \right.$ , in the absence of spin-orbit interaction D and the inhomogeneity parameter b. Therefore, it is possible to perform quantum teleportation protocol $\mathcal{T}_0$ and entanglement teleportation $\mathcal{T}_1$ , with perfect quality, by choosing a proper set of parameters and employing one of these maximally entangled robust states as the initial state of the resource.

Effects of Dzyaloshinski–Moriya interaction and intrinsic decoherence on teleportation via a two-qubit Heisenberg XYZ model

Quantum teleportation via the entangled channel composed of a two-qubit Heisenberg XYZ model with Dzyaloshinski–Moriya (DM) interaction in the presence of intrinsic decoherence has been investigated. We find that the initial state of the channel plays an important role in the teleported state and the average fidelity of teleportation. When the initial channel is in the state |Ψ1(0)〉 = a|00〉 + b|11〉, the average fidelity is equal to 1/3 constantly, which is independent of the DM interaction and the intrinsic decoherence effect. But when the channel is initially in the state |Ψ2(0)〉 = c|01〉 + d|10〉, the average fidelity is always larger than 2/3. Moreover, under a certain condition, the average fidelity can be enhanced by adjusting the DM interaction, and the intrinsic decoherence leads to a suppression of the fluctuation of the average fidelity.

INFLUENCE OF INTRINSIC DECOHERENCE ON THE ENTANGLEMENT BETWEEN TWO ATOMS IN TAVIS–CUMMINGS MODEL

Considering the dipole–dipole coupling intensity between two atoms and the field in the Fock state, the entanglement dynamics between two atoms that are initially entangled in the Tavis–Cummings model with intrinsic decoherence have been investigated. The two-atom entanglement appears with periodicity without considering intrinsic decoherence. However, the intrinsic decoherence causes the decay of entanglement between two atoms, with the decrease of the intrinsic decoherence coefficient, the entanglement will quickly become a constant value, which is affected by the two-atom initial state, the dipole–dipole coupling intensity and the field in the Fock state. Meanwhile, the two-atom quantum state will stay forever in the maximal entangled state when the initial state is proper, even in the presence of intrinsic decoherence. Furthermore, the two atoms can generate maximal entangled state even if they are initially separated by adjusting the dipole–dipole interaction, the strong coupling can improve the value of entanglement.

Intrinsic decoherence effects on quantum dynamics of the nondegenerate two-photon f-deformed Jaynes–Cummings model governed by the Milburn equation

In this paper, we study the influence of the intrinsic decoherence on quantum statistical properties of a generalized nonlinear interacting atom–field system, i.e., the nondegenerate two-photon f-deformed Jaynes–Cummings model governed by the Milburn equation. The model contains the nonlinearities of both the cavity–field and the atom–field coupling. Until now, very few exact solutions of nonlinear systems that include a form of decoherence have been presented. The main achievement of the present work is to find exact analytical solutions for the quantum dynamics of the nonlinear model under consideration in the presence of intrinsic decoherence. With the help of a supersymmetric transformation, we first put the model Hamiltonian into an appropriate form for treating the intrinsic decoherence. Then, by applying the superoperator technique, we find an exact solution of the Milburn equation for a nondegenerate two-photon f-deformed Jaynes–Cummings model. We use this solution to investigate the effects of the intrinsic decoherence on temporal evolution of various nonclassical properties of the system, i.e., atomic population inversion, atomic dipole squeezing, atom–field entanglement, sub-Poissonian photon statistics, cross correlation between the two modes and quadrature squeezing of the cavity field. Particularly, we compare the numerical results for three different cases of two-mode deformed, one-mode deformed, and nondeformed Jaynes–Cummings models. PACS Nos.: 42.50.Ct, 42.50.Dv, 03.65.Yz

Coherent control in the presence of intrinsic decoherence: proton transfer in large molecular systems.

An efficient semiclassical approach is developed and used to calculate the coherent-control map and time dependent decoherence measure for the excited-state proton transfer dynamics associated with the keto-enolic tautomerization reaction of 2-(2'-hydroxyphenyl)-oxazole. The method extends the usual bichromatic coherent-control scenario to simulate control at finite times after photoexcitation of the system. Extensive coherent control is demonstrated in a large molecule despite the ultrafast decoherence phenomena, providing results of broad theoretical and experimental interest.