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Since the first preparation of a single trapped, laser-cooled ion by Neuhauser et al. in
1980, a continuously increasing degree of control over the state of single ions has been
achieved, such that what used to be spectroscopy has turned into coherent manipulation of
the internal (electronic) state, while laser cooling has evolved into the control of the
external degree of freedom, i.e. of the motional quantum state of the ion in the trap.
Based on these developments, Cirac and Zoller proposed in 1995 to use a trapped ion
string for processing quantum information, and they described the operations required to
realise a universal two-ion quantum logical gate. This seminal proposal sparked intense
experimental activities in many groups and has led to spectacular results.
In this lecture, the basic experimental techniques which enable quantum
information processing with trapped ions and atoms will be reviewed. In particular, the
fundamental concepts of quantum computing, such as quantum bits (qubits), qubit
rotations, and quantum gates, translate into experimental procedures in a quantum optics
laboratory will be explained.
Furthermore, the recent progress of quantum computing with ions and atoms
will be summarised, and some of the new approaches to meet future challenges will be
mentioned.
It is intended to provide an intuitive understanding of the matter that should
enable the non-specialist student to appreciate the paradigmatic role and the potential
of trapped single ions and atoms in the field of quantum computation.
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