Optical lattices and Quantum Information

A system of neural atoms stored in an optical lattice as shown in the figure below is a promising candidate for implementing scalable quantum computing. In this research project the leading European groups in the field conduct a concerted research effort towards making quantum information in optical lattices viable. Following their initial work, these groups have shown experimentally and theoretically that a quantum phase transition can be used to prepare exactly one atom per lattice site, where each atom can be considered as quantum bit. Based on this so-called Mott-Insulator state several schemes for quantum computation have been proposed, including proposals for the creation of entanglement, computation with cluster states and quantum simulations. In this project we use a Mott insulator composed of single atoms as a quantum register, in which one can encode qu-bits in the single atoms on each lattice site and quantum gates can be implemented acting on different atoms of the lattice. This setup is schematically shown in the figure. Atoms can be manipulated either at the single particle level or collectively. Crucial advantages are i) the simple quantum-level structures of atoms; ii) the insulation of the neutral atoms from the environment which leads to a strong suppression of decoherence, and iii) the ability to trap and act on a very large ensemble of identical atoms. An impressive example of the flexibility of optical lattices is the use of the internal degrees of freedom of ground state neutral atoms in order to generate the quantum entanglement that is essential of many quantum information protocols. To generate entanglement, one requires an experimental system that can be prepared in a pure atomic state, with significant and coherently controlled interactions between the particles composing the pure state. Samples of Bose-Einstein condensates, or of Fermi degenerate gases, fulfil these requirements, and, therefore, they could provide an ideal experimental system for studying quantum entanglement.
The goal of this work is to make quantum processing viable by using neutral atoms trapped in optical lattices. We focus on different challenges: preparation and initialisation of a quantum register; addressing, manipulating and measuring on single sites; two-bit gates and compatible stable qubits; generation and characterisation of multi-particle entanglement states; strategies for minimising decoherence; quantum simulator; new theoretical strategies for quantum computers with optical lattices. The final objectives of the project will provide a persistent and long-term commitment to emerging applications.

Investigators:  D. Jaksch
Collaborators:  E. Arimondo (Co-ordinator) , I. Bloch, H.-J. Briegel, T. Esslinger and P. Zoller
Home page:  http://olaqui.df.unipi.it/
Acronym:  OLAQUI
Funded by:  EU Specific Targeted Research Project; Call: FP6-2002-IST-C, Fet Open; Contract No 013501
Start date:  2005-02-01
End date:  2008-07-31

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