Multiparticle entanglement of hot trapped ions

We propose an efficient method to produce multiparticle entangled states of ions in an ion trap for which a wide range of interesting effects and appl ications have been suggested. Our preparation scheme exploits the collectiv e vibrational motion of the ions, but it works in such a way that this moti on need not be fully controlled in the experiment. The ions may, e.g., be i n thermal motion and exchange mechanical energy with a surrounding heat bat h without detrimental effects on the internal state preparation. Our scheme does not require access to the individual ions in the trap. [S0031-9007(99 )08580-4].