Optics Communications 402 (2017) 80–84 Contents lists available at ScienceDirect Optics Communications journal homepage: www.elsevier.com/locate/optcom Entanglement transfer from entangled non-linear coherent states of trapped ions to separable qubits Davood Afshar *, Azam Anbaraki, Mojtaba Jafarpour Department of Physics, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran article info Keywords: Entanglement transfer Nonlinear coherent states Trapped ion abstract In this paper, we consider the possibility of transferring entanglement from two-mode superposed nonlinear coherent states of trapped ions to separable qubits. Separable qubits are assumed to be in the ground state and each mode of the field states interacts with each one of the qubits under Jaynes–Cummings model. We find that there is an explicit dependence between the amount of transferred entanglement to the qubits and Lamb–Dicke parameter of the field states. Moreover, there is a correlation between the entanglement of qubits after interaction and the entanglement strength of the field states before that. In fact, qubits will have maximum amount of entanglement after the interaction with the maximally entangled field states in some ranges of the coherent amplitude, periodically. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Entanglement is a manifestation of quantum correlations which has no classical counterpart. Study of entanglement is of vital importance due to its application in quantum information theory, including dense coding [1] and quantum teleportation [2]. Entanglement may be achieved through local or nonlocal methods. One of the nonlocal methods to produce entanglement between two particles without having any interaction in the past is entanglement swapping [3–6]. A local method for producing entanglement is en- tanglement transfer from a quantum system to another one. Although entangled continuous variable states are important sources in quantum information processing [1,2], entangled qubit states have been preferred due to the possibility of simple manipulation of the stored information in them [7,8]. Hence, entanglement transfer from entangled continuous variable states to separable qubits merits scrutinization [9–15]. This transfer can be described by Jaynes–Cummings model, which considers the interaction between field states and the qubits which are shared between two similar cavities. In this paper, entangled nonlinear coherent states of trapped ions have been assumed as the field states and the entanglement transfer to a pair of separable qubits has been investigated using Jaynes–Cummings model. We consider the motion of ions in a Paul trap, in which charge particles are affected by a combination of static and oscillating electric fields [16]. Nonlinear coherent states of trapped ions motion can be * Corresponding author. E-mail address: da_afshar@yahoo.com (D. Afshar). generated by driving them using two lasers in the resolved sideband limit and far from the Lamb–Dicke regime [17,18]. The frequencies of two lasers are tuned to an electronic transition and first red motional sideband. After the interactions of the trapped ion with the two lasers, the stationary state of the system constitutes of an atomic ground state and a motional state of which the latter could be a nonlinear coherent state of trapped ion [17,18]. The structure of the rest of this paper is as follows. In Section 2, the entanglement of superposed two-mode non-linear coherent states of trapped ions will be studied. In Section 3, we will consider the interaction between field states and the separable qubits under Jaynes– Cummings model and examine their entanglement after this interaction. Finally, Section 4 is devoted to results and discussion. 2. Entanglement of superposed two-mode nonlinear coherent states Nonlinear coherent states have been introduced as follows [19]: |, ⟩ =   ∞ ∑ =0   [ ()]! √ ! |⟩ (1) where, the normalization constant,   , and  ()! are given by:   = { ∞ ∑ =0 || 2 [ ()  † ()]! ! } − 1 2 (2) http://dx.doi.org/10.1016/j.optcom.2017.05.054 Received 28 March 2017; Received in revised form 18 May 2017; Accepted 19 May 2017 0030-4018/© 2017 Elsevier B.V. All rights reserved.