Atom-cavity Entanglement Research Articles

Simulation of state transfer from atom to cavity radiation in atom-photon interaction in large detuning

In this research, atom-cavity entanglement in closed Jaynes – Cumming model has been used with the assumption of large detuning between atom and cavity, to simulate the state transfer from atom to cavity radiation. A two-level atom which is prepared in a half-half superposition between the ground and excited states, has been exposed to initially coherent radiation field which is far from resonance with the atom. Mixture of each subsystem, linear entropy, entanglement, Von Neumann entropy and Schmidt decomposition of composite system as a function of time, has been determined analytically, for the first time. Assuming large frequency differences between atom and radiation, the simulation is shown no energy is transferred between atom and radiation due to large detuning, even though atom-radiation entanglement took place. Also, it has been shown that a particular measurement on the atom in this composite entangled system, can project the composite system into a separable (non-entangled) state so that the radiation state is changed into a superposition of the coherent state which is called the cat state. The conditions required to transfer radiation into odd and even cat states have been particularly investigated.

Noise-assisted quantum coherence protection in a hierarchical environment

In this paper, we investigate coherence protection of a quantum system coupled to a hierarchical environment by utilizing noise. As an example, we solve the Jaynes-Cummings (J-C) model in presence of both a classical and a quantized noise. The master equation is derived beyond the Markov approximation, where the influence of memory effects from both noises is taken into account. More importantly, we find that the performance of the coherence protection sensitively depends on the non-Markovian properties of both noises. By analyzing the mathematical mechanism of the coherence protection, we show the decoherence caused by a non-Markovian noise with longer memory time can be suppressed by another Markovian noise with shorter memory time. Last but not least, as an outlook, we try to analyze the connection between the atom-cavity entanglement and the atomic coherence, then discuss the possible clue to search for the required noise. The results presented in this paper show the possibility of protecting coherence by utilizing noise and may open a new path to design noise-assisted coherence protection schemes.

Entanglement Evolution of Jaynes-Cummings Model in Resonance Case and Non-resonance Case

We investigate the entanglement evolution of a two-level atom and a quantized single model electromagnetic filed in the resonance and non-resonance cases. The effects of the initial state, detuning degree, photon number on the entanglement are shown in detail. The results show that the atom-cavity entanglement state appears with periodicity. The increasing of the photon number can make the period of quantum entanglement be shorter. In the non-resonant case, if we choose the suitable initial state the entanglement of atom-cavity can be 1.0

Geometric phase as entanglement probe in a pumped three-level atom placed near a dielectric

We introduce new features of the connection between entanglement induced by interaction and geometric phase acquired by a composite quantum system. Geometric phase, that reflects Bell angle between input and output photons in atom-cavity interaction, for a bipartite system under the inuence of a dielectric of Lorentzian permitti vity, is examined. We show that, with adjustment of Bell angle, typical features of atom-cavity entanglement can be obtained by considering a three- level appropriately positioned with respect to macroscopic bodies. We find that, due to the strong non-Mark ovian memory effects, phase Rabi oscillations, a principal signature of strong symmetrically or antisymmetrically photons evolution, ar e stimulated with atom farther from a medium with low oscillation frequency. On death of Rabi oscillations, which means symmetric entangled photons, a strong long-time-scale atom-cavity entanglement can be produced, specially, below the band gap region where the radiative decay dominates. This feature conicts the case of pure vacuum where atom-cavity entanglement decays exponentially. The feature that, our system is acting as a beam splitter (BS), is also, in detail, discussed. The results are of strong applications in constru ction of the universal quantum logic gates.

Entanglement properties of two atoms interacting with weak coherent states trapped in two distant cavities connected by an optical fiber

Considering a system comprised of two-level atoms resonantly interacting with weak coherent states trapped in two distant cavities connected by an optical fiber initially, we study the entanglement properties of the atom-atom, the cavity-cavity and the atom-cavity. Then the influences of the ratio between fiber-cavity and atom-cavity coupling intensity, the intensity and the phase of the cavity field on the entanglement properties are investigated numerically. It is shown that the entanglements of the atom-atom, the cavity-cavity and the atom-cavity vary with time in the periodical or approximately periodical manner; the entanglement can be transferred from cavity-cavity to atom-atom reciprocally. Compared with the entanglements of atom-atom and cavity-cavity, the varying period of atom-cavity entanglement is short. The ratio of fiber-cavity coupling intensity to atom-cavity coupling intensity and the phase of cavity field affect the entanglement properties greatly. The great entanglement can be achieved by using a smaller ratio of coupling intensity between fiber-cavity and atom-cavity.

The entanglement properties in the system of a two three-level atoms trapped in coupled cavities

We study the entanglement dynamics of the system composed of a Λ-type atom and a V-type atom resonantly interacting with two coupled cavities. The evolution of the state vector of the system is given. We investigate the evolutions of atom-atom entanglement, cavity-cavity entanglement, and atom-cavity entanglement by Negativity. The influences of cavity-cavity coupling coefficient on the entanglements are discussed. The results obtained by the numerical method show that the atom-atom entanglement is strengthened and the cavity-cavity entanglement is weakened with the increase of the cavity-cavity coupling coefficient.

原子与耦合腔相互作用系统中的纠缠特性

The two-excitation system comprising two two-level atoms resonantly interacting with two coupled cavities is analyzed.The evolution of the state vector of the system is given when the total excitation number equals two.By means of the numerical calculations,the temporal evolution in the entanglement is investigated between the atoms,between the cavities,as well as between the atom and the local cavity mode.The influences of coupling constant between cavities on the entanglements are discussed.The results obtained show that atom and atom are separable,and the cavity-cavity entanglement and the atom-cavity entanglement are weakened with increasing of the coupling constant between cavities.

The Entanglement Properties Induced by Atoms in Two Separate Cavities Connected by an Optical Fiber

We study the entanglement evolution between two atoms, which are initially entangled with a third atom and trapped in two separated cavities coupled by an optical fiber. We also investigate the temporal evolution in the entanglement between the atom and the local cavity mode. The influence of the state-selective measurement on the atom outside the cavities and the influence of cavity-fiber coupling coefficient on the entanglement are discussed. The results show that the entanglement can be strengthened through the state-selective measurement on the atom outside the cavities. We also find that, by increasing the cavity-fiber coupling coefficient, the atom-atom entanglement is strengthened, but the atom-cavity entanglement is weakened.

Entanglement properties in the system of atoms interacting with coupled cavities

We study the entanglement dynamics of the system composed of two two-level atoms resonantly interacting with two coupled cavities. The evolutions of atom-atom entanglement, cavity-cavity entanglement and atom-cavity entanglement are investigated. The influence of coupling constant between cavities on entanglement property is discussed. The numerical results show that atom-atom entanglement property is strengthened while atom-cavity entanglement property and cavity-cavity entanglement property are weakened with the increasing of the coupling constant between cavities.

Environment induced entanglement in cavity-QED

The effects of dissipative dynamics on the magnitude of entanglement generated In atom-photon interactions inside cavities is studied. We present some concrete examples of environment Induced entanglement in alom-photon interactions. We consider various dissipative atom-cavity systems and show that their collective dynamics can be used to maximize entanglement for intermediate values of the cavity leakage parameter κ. We first consider the interaction of a single two-level atom with one of two coupled microwave cavities and show analytically that the atom-cavity entanglement increases with cavity leakage. We next consider a system of two atoms passing successively through a cavity and derive the expression for the maximum value of in terms of the Rabi angle gt, for which the two-atom entanglement can be Increased. Finally, numerical investigation of micromaser dynamics also reveals the increase of two-atom entanglement with stronger cavity-environment coupling for experimentally attainable values of the micromaser parameters.

Adiabatic entanglement in two-atom cavity QED

We analyse the problem of a single mode field interacting with a pair of two level atoms. The atoms enter and exit the cavity at different times. Instead of using constant coupling, we use time dependent couplings which represent the spatial dependence of the mode. Although the system evolution is adiabatic for most of the time, a previously unstudied energy crossing plays a key role in the system dynamics when the atoms have a time delay. We show that conditional atom-cavity entanglement can be generated, while for large photon numbers the entangled system has a behaviour which can be mapped onto the single atom Jaynes-Cummings model. Exploring the main features of this system we propose simple and fairly robust methods for entangling atoms independently of the cavity, for quantum state mapping, and for implementing SWAP and C-NOT gates with atomic qubits.

Environment-assisted entanglement enhancement

We consider dissipative atom-cavity systems and show that their collective dynamics leads to the maximization of entanglement for intermediate values of the cavity leakage parameter $\kappa$. We discuss possible ways the reservoir influences entanglement. We first consider the entanglement of a single two-level atom with a microwave cavity that is coupled to another cavity. We show that the atom-cavity entanglement can be made to increase with cavity leakage. We next show that the entanglement between two atoms passing successively through a cavity can be maximised for intermediate values of $\kappa$. We finally consider the micromaser where the increase of two-atom entanglement for stronger cavity-environment coupling is demonstrated for experimentally attainable values of the micromaser parameters.