Ion Crystals for Quantum Information Processing

We investigate experimentally quantum information processing using a string of trapped ions where each ion represents a bit of quantum information (qubit). We report on the realization of the Cirac Zoller universal control-NOT gate with a two-ion crystal. Quantum gates between the ions are realized by coupling them through their collective quantized motion. We show that the control ion's qubit state determines the evolution of the target ion's qubit state. Additionally, we report on a tomographic method to fully characterize the quantum state of a qubit register. Using this tomographic method we investigate Bell states which we generate in a two-qubit system and quantify their entanglement.