Generation of Dicke States with Phonon-Mediated Multi-level Stimulated   Raman Adiabatic Passage
  We generate half-excited symmetric Dicke states of two and four ions. We use multi-level stimulated Raman adiabatic passage (STIRAP) whose intermediate states are phonon Fock states. This process corresponds to the spin squeezing operation and half-excited Dicke states are generated during multi-level STIRAP. This method does not require local access for each ion or the preparation of phonon Fock states. Furthermore, it is robust since it is an adiabatic process. We evaluate the Dicke state using a witness operator and determine the upper and lower bounds of the fidelity without using full quantum tomography. 
Atsushi Noguchi, Kenji Toyoda, Shinji Urabe
quant-ph