Entanglement between artificial atoms and photons of lossless cavities (original) (raw)
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We investigate some aspects of the dynamics and entanglement of bipartite quantum system (atom-quantized field), coupled to a third “external” subsystem (quantized field). We make use of the Raman coupled model; a three-level atom in a lambda configuration interacting with two modes of the quantized cavity field. We consider the far off resonance limit, which allows the derivation of an effective Hamiltonian of a two-level atom coupled to the fields. We also make a comparison with the situation in which one of the modes is treated classically rather than prepared in a quantum field (coherent state).
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Physics Letters A, 2017
We study the dynamical entanglement of two identical atoms interacting with a quantum field. As a simplified model for this physical system we consider two harmonic oscillators linearly coupled to a massless scalar field in the dressed coordinates and states approach and enclose the whole system inside a spherical cavity of radius R. Through a quantity called concurrence, the entanglement evolution for the two-atom system will be discussed, for a range of initial states composed of a superposition of atomic states. Our results reveals how the concurrence of the two atoms behaves through the time evolution, for arbitrary cavity size and for arbitrary coupling constant, weak, intermediate or strong. All our computations are exact and only the final step is numerical. These numerical solutions give us fascinating results for the concurrence, such as quasi-random fluctuations, with a resemblance of periodicity. Another interesting result we found is when the system is initially maximally entangled (disentangled), after the time t = 2R, the system becomes again strongly entangled (disentangled) particularly during the first oscillations, later this phenomenon could be wrecked depending on the initial condition. We also show the concurrence after a too long time elapsed with a good precision.
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An open quantum bipartite system consisting of two independent two-level atoms interacting nonlinearly with a two-mode electromagnetic cavity field is investigated by proposing a suitable non-Hermitian generalization of the Hamiltonian. The mathematical procedure of obtaining the corresponding wave function of the system is clearly given. Pancharatnam phase is studied to give a precise information about the required initial system state, which is related to artificial phase jumps, to control the degree of entanglement (DEM) and get the highest concurrence. We discuss the effect of time-variation coupling, and dissipation of both atoms and cavity. The effect of the time-variation function appears as frequency modulation (FM) effect in the radio waves. Concurrence rapidly reaches the disentangled state (death of entanglement) by increasing the effect of field decay. On the contrary, the atomic decay has no effect. 1. Inroduction Quantum systems promise enhanced capabilities in sensing, communications, and computing beyond what can be achieved with classical-based conventional technologies rather than quantum physics. Mathematical models are essential for analyzing these systems and building suitable quantum models from empirical data is an important research topic. In Dirac theory of radiation [1], he considered atoms and the radiation field with which they interact as a single system whose energy is represented by the frequency/energy of each atom solely, the frequency/energy of every mode of the applied laser field alone, and a small term is to the coupling energy between atoms and field modes. The interaction term is necessary if atoms and field modes are to affect each other. A simple model is that we consider a pendulum of resonant frequency ω 0 , which corresponds to an atom, and a vibrating string of resonant frequency ω 1 which corresponds to the radiation field. Jaynes-Cummings model (JCM) [2] is the first solvable analytical model to represent the atom-field interaction with experimental verification [3]. JCM has been subjected to intensive research in the last decades with many interesting phenomena explored [4-7]. The matter-field coupling term may be constant [8-10] or time-dependent [11,12], and that depends on the considered physical situation.