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RESEARCH PRODUCT

Quantum Information by Adiabatic Passage : Quantum Gates and Decoherence

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The first part of this thesis is about adiabatic quantum processes designed for the implementation of quantum logic gates, the elementary components of quantumcomputers, by the interaction of pulsed laser fields with atoms. The adiabaticmethods allow robust processes, i.e. which are not sensitive to the fluctuationsof experimental parameters. The processes described in this thesis only requireaccurate control of the polarisations and the relative static phases of thelaser fields. These processes allow the implementation of a universal set ofquantum gates, which make possible the implementation of all the other quantumgates by combinations.The second part of this thesis concerns the effects of dephasing decoherence inadiabatic passage. The transition probability formula of a two level system withdephasing is established. This formula is valid in all regimes, from diabatic toadiabatic, and can be used to derive the parameters of elliptic trajectoriesthat optimise the population transfer.