S. Guérin

Robust coherent superposition of states by single-shot shaped pulse

We adapt a single-shot shaped pulse technique to produce robust coherent superpositions of quantum states with a high fidelity of control. We derive simple pulses of low areas for the corresponding Rabi frequency which are robust with respect to pulse area imperfections. Such features of robustness, high-fidelity, and low Rabi frequency area are crucial steps towards the experimental implementation of scalable quantum gates.

Shaping coherent excitation of atoms and molecules by a train of ultrashort laser pulses

We propose a mechanism to produce a superposition of atomic and molecular states by a train of ultrashort laser pulses combined with weak control fields. By adjusting the repetition rate of the pump pulses and the intensity of the coupling laser, one can suppress a transition while simultaneously enhancing the desired transitions. As an example, various superpositions of vibrational states of the K{sub 2} molecule are shown.

Deterministic source of a train of indistinguishable single-photon pulses with a single-atom-cavity system

We present a mechanism to produce indistinguishable single-photon pulses on demand from an optical cavity. The sequences of two laser pulses generate, at the two Raman transitions of a four-level atom, the same cavity-mode photons without repumping of the atom between photon generations. Photons are emitted from the cavity with near-unit efficiency in well-defined temporal modes of identical shapes controlled by the laser fields. The second-order correlation function reveals the single-photon nature of the proposed source. A realistic setup for the experimental implementation is presented.

Superposition of states by adiabatic passage in N-pod systems

We study the stimulated Raman adiabatic passage technique in an N-pod system driven by N pulsed fields when N-2 and N-1 pulses not connected to the initial state have the same shape. We show that, for properly timed pulses, robust population transfer from an initial ground state to an arbitrary coherent superposition of the ground states can be achieved in a single step. The case of N-2 pulses of the same shape involves a geometric phase of the same type as the one appearing in tripod systems.

Nonlinear Stimulated Raman Exact Passage by Resonance-Locked Inverse Engineering

We derive an exact and robust stimulated Raman process for nonlinear quantum systems driven by pulsed external fields. The external fields are designed with closed-form expressions from the inverse engineering of a given efficient and stable dynamics. This technique allows one to induce a controlled population inversion which surpasses the usual nonlinear stimulated Raman adiabatic passage efficiency.

Superluminal pulse propagation in a non-linear Λ-type atomic medium

Propagation of two optical pulses in a non-linear Λ-type atomic medium is considered. The analytical solution to the self-consistent Maxwell-Schrodinger equations in the adiabatic following condition is obtained. Superluminal effects during propagation of pulses in the medium are studied.