Showing papers by "Stéphane Guérin published in 2006"

Field-free one-dimensional alignment of ethylene molecule

Abstract: We report an experimental study of nonadiabatic laser-induced molecular alignment of ethylene (C{sub 2}H{sub 4}) using a linearly polarized short laser pulse of moderate intensity. The information about the confinement of the C=C bond axis along the direction of the applied electric field is obtained by measuring the depolarization of a second short pulse of weak intensity interacting with the molecules after they have been exposed to the first pulse. The experimental data are compared with the numerical simulation of the Schroedinger equation written for the nonresonant interaction of an asymmetric top rigid rotor with a linearly polarized electric field. The field-free alignment is described by analyzing the time evolution of the angular distribution of the molecular axes together with the expectation value of the relevant squared direction cosine matrix elements.

Arbitrary state controlled-unitary gate by adiabatic passage

Abstract: We propose a fast scheme involving atoms fixed in an optical cavity to directly implement the universal controlled-unitary gate. The present technique based on adiabatic passage uses dark states well suited for the controlled-rotation operation. We show that these dark states allow the robust implementation of a gate that is a generalization of the controlled-unitary gate to the case where the control qubit can be selected to be an arbitrary state. This gate has potential applications to the rapid implementation of quantum algorithms such as the projective measurement algorithm. This process is decoherence-free since excited atomic states and cavity modes are not populated during the dynamics.

CNOT gate by adiabatic passage with an optical cavity

Abstract: We propose a scheme for the construction of a CNOT gate by adiabatic passage in an optical cavity. In opposition to a previously proposed method, the technique is not based on fractional adiabatic passage, which requires the control of the ratio of two pulse amplitudes. Moreover, the technique constitutes a decoherence-free method in the sense that spontaneous emission and cavity damping are avoided since the dynamics follows dark states.