Abstract

Trapped and laser-cooled atomic ions have provided an interesting system for the study of quantum entanglement, quantum information, and decoherence. Here, the atom's internal states can be entangled with their (harmonic) quantized motional modes through a coupling provided by inhomogeneous (classical) electromagnetic fields. This coupling is analogous to the Jaynes-Cummings coupling between atomic internal states and (harmonic) modes of the quantized electromagnetic field in Cavity-QED. We have used this basic source of entanglement to implement the elements of quantum-information processing as suggested by Cirac and Zoller (1995). In recent experiments at NIST, we have applied these techniques to the study of entanglement-enhanced measurements (spin squeezing), measurement of Bell's inequalities with efficient detection, decoherence, and decoherence-free subspaces (DFS). The ion trap system is, in principle, scable to arbitrarily large number of ions. Current efforts are devoted to realizing this scaling by using a multiplexed system of interconnected ion traps, a kind of "quantum-CCD."

© 2001 Optical Society of America