Experimental Quantum Computation
with Ion Traps
(with Prof.
D.Stacey and Prof. A.Steane)
Experimental methods in atomic physics and quantum optics
are currently among the most precise available in physics or any other
science. It is now possible to manipulate and measure single atoms, or small
groups of atoms, by first confining them by electromagnetic potentials —
making a so-called atom or ion ‘trap’— and then illuminating them with pulses
of laser light of controlled frequency and duration.
The importance of the ion trap for quantum information
processing is that it is the only method which allows complete control of an
isolated several-qubit quantum system using current technology. Individual
ions can be probed and re-set at will, which allows active stabilization of
the system by probing for errors and correcting them.
We have recently built and are currently running such a
device. The major research aims are to demonstrate new methods which we have
proposed to probe the quantum states, and to achieve quantum processing among
the ions, especially quantum error correction. We aim to study open questions
in the fundamental theory of quantum computing, going beyond basic
demonstration experiments.
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Key Publications
Experimental demonstration of a robust, high-fidelity
geometric two ion-qubit phase gate.
Leibfried, D. et al.
Nature 422 412-5
(2003).
The highest-fidelity experimental quantum logic gate yet demonstrated (work
carried out at NIST Ion Storage group, Boulder, USA).
Oxford ion-trap quantum computing project.
Lucas, D.M. et al.
Phil.Trans.R.Soc.Lond. A361 1401-8 (2003).
Review of the Oxford research project, including results on qubit read-out
and photoionization trap loading.
Isotope-selective photoionization for calcium ion trapping.
Lucas, D.M. et al.
Phys.Rev. A69 012711 (2004).
A detailed experimental study of photoionization ion trap loading, and
the first laser-cooling experiments with an odd isotope of Ca+.
The direct detection of one quantum of angular momentum.
McDonnell, M.J. et al.
[to be published].
Reliable “single-shot” detection of the spin direction of a single atom.
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