The influences of dipole-dipole interaction and detuning on the sudden death of entanglement between two atoms in the Tavis-Cummings model

The influences of dipole-dipole interaction and detuning on the entanglement between two atoms with different initial tripartite entangled W-like states in the Tavis Cummings model have been investigated by means of Wootters＇ concurrence, respectively. The results show that the entanglement between the two atoms can be enhanced via appropriately tuning the strength of dipole-dipole interaction of two atoms or the detunings between atom and cavity, and the so-called sudden death effect can he weakened simultaneously.

Relation between initial conditions and entanglement sudden death for two-qubit extended Werner-like states

In this paper, the dynamical behavior of entanglement of an uncoupled two-qubit system, which interacts with inde- pendent identical amplitude damping environments and is initially prepared in the extended Werner-like （EWL） states, is investigated. The results show that whether entanglement sudden death （ESD） of an EWL state will occur or not depends on initial purity and concurrence. The boundaries between ESD states and ESD-free states for two kinds of EWL states are found to be different. Furthermore, some regions are shown where ESD states can be transformed into ESD-free states by local unitary operations.

Sudden death and revival of entanglement of two qubits coupled collectively to a thermal reservoir

In this paper, we investigate the entanglement of two qubits coupled collectively to a common thermal environment and find that the the collective decay can lead to a revival of the entanglement that has already been destroyed. We also show that the ability of the system to revival entanglement relies on the mean photon number of the thermal environment and the degree of entanglement of the initial state.

Sudden birth versus sudden death of entanglement for the extended Werner-like state in a dissipative environment

In this paper, we investigate the dynamical behaviour of entanglement in terms of concurrence in a bipartite system subjected to an external magnetic field under the action of dissipative environments in the extended Werner-like initial state. The interesting phenomenon of entanglement sudden death as well as sudden birth appears during the evolution process. We analyse in detail the effect of the purity of the initial entangled state of two qubits via Heisenberg XY interaction on the apparition time of entanglement sudden death and entanglement sudden birth. Furthermore, the conditions on the conversion of entanglement sudden death and entanglement sudden birth can be generalized when the initial entangled state is not pure. In particular, a critical purity of the initial mixed entangled state exists, above which entanglement sudden birth vanishes while entanglement sudden death appears. It is also noticed that stable entanglement, which is independent of different initial states of the qubits （pure or mixed state）, occurs even in the presence of decoherence. These results arising from the combination of the extended Werner-like initial state and dissipative environments suggest an approach to control and enhance the entanglement even after purity induced sudden birth, death and revival.

Optimal entropy squeezing sudden generation and its control for an effective two-level moving atom entanglement with the two-mode coherent fields

From the viewpoint of quantum information, this paper proposes a concept and a definition of the atomic optimal entropy squeezing sudden generation （AOESSG） for the system of an effective two-level moving atom which entangles with the two-mode coherent fields. It also researches the relationship between the AOESSG and entanglement sudden death of the atom-fields, and discusses the influences of atomic initial state on the AOESSG and obtains the system parameter which controls the AOESSG.

Control of Sudden Death of Entanglement by Transient Effects

我们面对短暂效果调查在一个孤立的原子和一个 JaynesCummings 原子之间的纠纷的性质。这些效果由于其明确的时间依赖为案例被考虑的联合的原子地的调整线性扫。我们证明纠纷的突然的死亡能被短暂效果控制。这些效果能及时压制纠纷的突然的死亡。

Sudden death of entanglement of a quantum model

In this paper the so-called sudden death effect of entanglement is investigated in a quantum model. The results show that one can expect the resurrection of the original entanglement to occur in a periodic way following each sudden death event. The length of the time interval for the zero entanglement depends not only on the degree of entanglement of the initial state but also on the initial state.

Sudden death of entanglement of two atoms interacting with thermal fields

We investigate the entanglement dynamics of two initially entangled atoms each interacting with a thermal field. We show that the two entangled atoms become completely disentangled in a finite time and that the lost information cannot return to the atomic system when the mean photon number of the thermal field exceeds a critical value （3.3584）, even though the whole system is lossless. Then we study how the detuning between the atomic transition frequency and the field frequency and the disparity between two coupling rates would affect the evolution of the entanglement of the atomic system.

Entanglement sudden death induced by the Dzialoshinskii-Moriya interaction

In this paper, we study the entanglement dynamics of two-spin Heisenberg XYZ model with the Dzialoshinskii- Moriya （DM） interaction. The system is initially prepared in the Werner state. The effects of purity of the initial state and DM coupling parameter on the evolution of entanglement are investigated. The necessary and sufficient condition for the appearance of the entanglement sudden death （ESD） phenomenon has been deduced. The result shows that the ESD always occurs if the initial state is sufficiently impure for the given coupling parameter or the DM interaction is sufficiently strong for the given initial state. Moreover, the critical values of them are calculated.

Entanglement sudden death of two atoms interacting with a cavity via the two-photon process in a strong-driving-assisted system

We examine the entanglement dynamics between two strongly driven atoms off-resonantly coupled with a singlemode cavity via the two-photon process with the help of negativity in two different types of initial states. The results show that entanglement sudden death may occur under both the above conditions and the sudden death effect can be monitored by modulating the atom-cavity detunings. Furthermore, we also find an atomic decoherence-free subspace so that the initial entanglement between two atoms remains invariable in application.

Control of entanglement sudden death by Kerr medium

The entanglement dynamics of system, where atoms A and B interact with single mode cavity fields a and b respectively, is studied. The interaction between atom A and cavity a may be described by using the typical Jaynes Cummings model, while that between the atom B and cavity b filled with a Kerr medium is of a two-photon process. For a certain initial atom entanglement state, there is an entanglement sudden death effect between the two atoms. The Kerr medium in the cavity b can effectively prevent the undesirable entanglement sudden death from occurring. Also, from the viewpoint of the population dynamics, we discuss why the Kerr medium can do so.

Three-Qubit Entanglement Sudden Death

我们经由否定性学习 three-qubit 系统的纠纷动力学。三原子 A， B，和 C 与他们的自己的贾内斯·卡明斯洞 isolatedly 交往一， b，和 c。Aa 系统被准备然而，与 Bb 和 Cc 纠缠了他们的相互的隔离禁止与系统 Bb 和 Cc 交往的 Aa。它是为系统 Bb 和 Cc 的一样。我们显示出不同 three-qubit 系统 ABC， abc， Abc，和 aBC 的纠纷进化并且发现纠纷突然的死亡效果。

Distillability sudden death in a two qutrit systems under a thermal reservoir

The dynamics of distillability entanglement between qutrit-qutrit systems interacting with a thermal reservoir is investigated in this paper. We discovered an interesting phenomenon that under a thermal reservoir certain initially prepared free=entangled states become bound-entangled states in a finite time, which is called distillability sudden death （DSD）. We use a realignment criterion to measure the nine-dimensional density matrix of the entanglement. Moreover, we analyze some other parameters to investigate the effects to the systems. Explanations are then given.

Decoherence-free subspace and entanglement sudden death of multi-photon polarization states in fiber channels

The construction of quantum networks requires long-distance teleportation of multi-qubit entangled states.Here,we investigate the entanglement dynamics of GHZ and W states in fiber channels.In a fiber channel,the two most important phenomena that affect polarization entanglement are polarization mode dispersion(PMD)and polarization-dependent loss(PDL).We theoretically characterize how PMD and PDL vectors affect three-qubit states.In particular,upon quantifying the entanglement at the output states using concurrence and entanglement witnesses,we reveal the occurrence of entanglement sudden death and the appearance of decoherence-free subspaces in tripartite systems.Finally,we explore the evolution of GHZ and W state with an arbitrary number of photons in a fiber network and discuss the decoherence mechanism of the 4-party cluster state.

Entanglement dynamics between an isolated atom and a moving atom in the cavity

The entanglement dynamics between an isolated atom and a moving atom interacting with a cavity field is investigated. The results show that there appears sudden death of entanglement between the isolated atom and the moving atom and that the time of entanglement sudden death （ESD） is independent of the initial state of the system. It is interesting that the isolated atom can also entangle with a cavity field, though they do not interact with each other originally, which stems from the fact that the entanglement between the isolated atom and the moving atom may turn into the entanglement between the isolated atom and the cavity.

Time of Conception and Birth-Relation of “Big Killers” Patients and Longevity

In recent years some interrelationships between time of birth and longevity were published. Concomitant publications appeared demonstrating links between Space Weather and the timing of medical events;in part of both these studies it was shown that Space Weather indices are stronger connected with the time of conception as with the birth time. The aim of these study was to consider birth and conception month of patients suffering from a number of “big killer” pathologies, affecting human longevity and comparing with published data on centenarians—100 - 112 years old persons in the USA. Patients and Methods: We included monthly births distribution of our four papers including patients with Acute Myocardial Infarction undergoing Percutaneous Coronary Intervention (PCI)—n-3765, and admitted in another tertiary medical facility for AMI—n-22,047, and, also patients suffering Rapid—n-1239 and Sudden Cardiac Death—n-327 and, also, patients with oncologic malignancies—n-44587. At all in this group 71,965 patients were included. Their birth and conception months were compared with analogical data of 1574 people of 100 - 112 years old using data of L.A. and N.S. Gavrilov for USA centenarians. Results: The birth months of the cardiovascular and oncology patients were maximal in January, March and April (above 10% at each of these months);their conception was maximal in April, June and July. The monthly distribution of conception and birth of the studied population is presented in Tables 1-3. The maximal birth months of the centenarians were November, September, and October;the maximal conception months were December, January, and February. Conclusion: People suffering Myocardial Infarction, Sudden Cardiac Death and Oncologic Malignancies are in higher numbers born in the first four months of the year and conception in April, June and July. The maximal birth months of the very old people were November, September and October and conception were December, January and February.

Entropy and Entanglement of Moving Two Atoms in a Squeezed Field via Four-Photon Process

In this paper, the entanglement between two atoms and squeezed field via four photon process is investigated. The dynamical behavior of the entanglement between two atoms and a squeezed field is analyzed. In particular, the effects of the atomic motion, the initial atomic state and the field squeezing are examined. A high amount of entanglement is generated by increasing the field squeezing. Furthermore, we show that a sudden death and sudden birth emerge when the moving atoms are initially prepared in the excited state.

Entanglement dynamics of two distant atoms in two detuning cavities

We investigate the entanglement dynamics via the concurrence of two distant atoms interacting off-resonantly with two cavity fields in Fock states, respectively. We find that the evolution of entanglement has sudden death and sudden birth phenomena, that with the increase of photon numbers in the two cavities, the alternate frequency of sudden death and sudden birth turns fast, and that the amplitude of concurrence oscillates regularly with oscillation frequency becoming slow when the cavity fields have the same photon numbers. While, the maximum of concurrence declines and the amplitude of concurrence oscillates irregularly when the two cavity fields have different photon numbers. In addition, we find the length of death time is dependent on the initial entanglement.

The entanglement of two moving atoms interacting with a single-mode field via a three-photon process

In this paper, the entanglement of two moving atoms induced by a single-mode field via a three-photon process is investigated. It is shown that the entanglement is dependent on the category of the field, the average photon number N, the number p of half-wave lengths of the field mode and the atomic initial state. Also, the sudden death and the sudden birth of the entanglement are detected in this model and the results show that the existence of the sudden death and the sudden birth depends on the parameter and the category of the mode field. In addition, the three-photon process is a higher order nonlinear process.

A study on entanglement dynamics for a four-qubit model

In this paper, we consider the entanglement dynamics of a four-qubit model [2006 Phys. Rev. A 74 042328] where two entangled qubits a and b locally interact with separate qubits A and B via the spin-exchange-like Hamiltonian. We study the effect of purity of initial entangled state of qubits a, b on the entanglement evolution and its relation with energy transfer. Also, we find that the total bipartite entanglement of qubits a, b plus A, B is not a constant any longer when the initial entangled state of a, b is not pure, which is a complement to the result in the paper [2007 J. Phys. B 40 S45] for the pure case.