A simple Scheme for Generating an n-Qubit W State in a Trapped-Ion System without a Lamb-Dicke Limit

A simple and scalable scheme is proposed to generate a n-qubit W state in a trapped-ion system without the Lamb--Dicke limit. The n-qubit W state can be generated by the interaction between the ions and the laser field if the collective mode is initially prepared in the single-phonon state and each ion is in the ground state. The scheme only requires a single laser and avoids laser manipulation of the individual ion. The time required to complete the process decreases with the number of ions. The present scheme is not limited to small values of the LD parameter, which greatly enhances operation speeds.