Abstract

Currently, the most promising physical system for the realization of a quantum computer is a collection of trapped atomic ions. Here, internal electronic states of the ions act as quantum bits, and with the use of quantum logic operations they are coupled through their collective motion in the trap.¹ At NIST, following the demonstration of rudimentary quantum logic gates² and related experiments³ with a single trapped ion, we have begun experiments with up to three ions. We have laser-cooled all modes of two ions⁴ and select modes of three ions to the ground state, thereby paving the way for subsequent quantum logic operations. We have also used quantum logic on two ions to engineer the Bell entangled states,⁵ representing the first source of entanglement not relying on a selection process. This type of deterministic entanglement is a crucial requirement for large-scale quantum computation. We continue to investigate the several technical problems with the ion trap quantum computer such as the decoherence of collective motion as well as issues dealing with the scale-up to larger numbers of ions. Supported by the U.S. National Security Agency, Office of Naval Research, and Army Research Office.

© 1999 Optical Society of America