Narrow Results

In this paper, the entanglement between two qubits that exist in two distinct cavities which are connected by an optical fiber is investigated by using the concurrence, while two-photon transitions and Kerr medium effect are also considered. Each cavity contains a qubit and a single-mode quantized field. The appearance of entanglement between the two qubits in the separate cavities originates from the presence of optical fiber. The obtained numerical results of the considered system show that, if the Kerr medium is large enough, the initial values of entanglement between the two qubits (which may have the maximum possible value, i.e. 1) can be approximately protected from the large amplitude fluctuations, so that acceptable stability is created. Also, qubit-field coupling and detuning effects are investigated and it is observed that symmetric coupling results in more stability of entanglement. Eventually, atomic population inversion is also studied and it is observed that it is controllable by considering different parameters.

In this paper we have investigated the dynamics of two cavities each with a two-level atom, coupled together with photon hopping. The coupled cavity system is studied in single excitation subspace and the evolution of the atom (field) states probabilities are obtained analytically. The probability amplitude of states executes oscillations with different modes and amplitudes, determined by the coupling strengths. The evolution is examined in detail for different atom field coupling strength, g and field–field hopping strength, A. It is noticed that the exact atomic probability amplitude transfer occurs when g ≪ A with minimal field excitation probability and the period of probability transfer is calculated. In the limit g ≫ A there exists periodic exchange of probability between atom and field inside each cavity and also between cavity 1 and cavity 2. Periodicity of each exchange in this limit also obtained.

We study the effect of Kerr type nonlinear medium in quantum state transfer (QST). We have investigated the effect of different coupling schemes and Kerr medium parameters $p$ and ${\omega }_K$. We found that the Kerr medium introduced in the connection channel can act like a controller for QST. The numerical simulations are performed without taking the adiabatic approximation. Rotating wave approximation is used in the atom–cavity interaction only in the lower coupling regime.

The interaction between identical two-level atoms with a system that consists of two coupled cavities connected by an optical fiber was investigated. With new bosonic operators, the interaction Hamiltonian between the fiber and the cavities can be diagonalized (Pellizzari's model¹). In the strong coupling regime (cavity field-fiber), the interaction between atoms and the non-resonant normal modes can be eliminated, simplifying our system to that of one atom interacting with a single-mode cavity. For this interaction, we have analyzed the entanglement between distant atoms. We present two simple procedures to generate two atoms in a maximally entangled state, interacting (i) successively and (ii) simultaneously with the coupled cavities system.

By controlling the parameters of the system, the effective interaction between different atoms is achieved in different cavities. Based on the interaction, scheme to generate three-atom Greenberger–Horne–Zeilinger (GHZ) is proposed in coupled cavities. Spontaneous emission of excited states and decay of cavity modes can be suppressed efficiently. In addition, the scheme is robust against the variation of hopping rate between cavities.