Search results for "quant-ph"

Sur le rôle des singularités hamiltoniennes dans les systèmes contrôlés : applications en mécanique quantique et en optique non-linéaire.

2012

This thesis has two goals: the first one is to improve the control techniques in quantum mechanics, and more specifically in NMR, by using the tools of geometric optimal control. The second one is the study of the influence of Hamiltonian singularities in controlled systems. The chapter about optimal control study three classical problems of NMR : the inversion problem, the influence of the radiation damping term, and the steady state technique. Then, we apply the geometric optimal control to the problem of the population transfert in a three levels quantum system to recover the STIRAP scheme.The two next chapters study Hamiltonian singularities. We show that they allow to control the polar…

Negatively Curved Nanographene with Heptagonal and [5]Helicene Units

2020

Negatively curved nanographene (NG) 4, having two heptagons and a [5]helicene, was unexpectedly obtained by aryl rearrangement and stepwise cyclodehydrogenations. X-ray crystallography confirmed the saddle-shaped structures of intermediate 3 and NG 4. The favorability of rearrangement over helicene formation following radical cation or arenium cation mechanisms is supported by theoretical calculations. NG 4 demonstrates a reversible mechanochromic color change and solid-state emission, presumably benefiting from its loose crystal packing. After resolution by chiral high-performance liquid chromatography, the circular dichroism spectra of enantiomers 4-(P) and 4-(M) were measured and showed …

Algebraic Study of XYn Molecules in Vibrationaly High Excited States

2008

Vibrational resonances in XYn non planar molecules: local versus normal modes formalism.

2007

L'influence de la nanosolvation sur la stabilité des peptides à l'étude du gaz

2013

ATOM-WALL COLLISIONS INFLUENCE ON DARKLINE ATOMIC RESONANCES IN SUBMICRON THIN VAPOUR CELLS.

2010

Recently it was demonstrated that miniaturization of alkali cells, i.e. the use of an extremely thin cell (ETC) for the applications using the electromagnetically induced transparency (EIT) effect, despite to intuitive expectation, does not cause a strong broadening of the dark-line (DL) linewidth. Here we present the conditions when a strong broadening of DL linewidth (more than by 10 times) can be easily observed due to atom-wall collisions influence and this could be a convenient and robust tool for atomwall (i.e. ETC's window material/temperature) collisions study. We present experimental and theoretical results on EIT realized in a Λ- system of 85Rb, D2 line, 5S-5P-5S for a Rb vapour c…

Landau‐Zener transition for association of an atomic Bose‐Einstein condensate with interparticle elastic interactions included.

2008

Qauntum control of molecular rotation and of processes in Nuclear Magnetic Resonance

2019

The goal of this thesis is to apply quantum control techniques to manipulate molecular rotation and to enhance the efficiency of processes in Nuclear Magnetic Resonance.These techniques have been used theoretically and experimentally to control the orientation of a symmetric top molecule by means of THz laser fields. This study has been extended to the case of a long interaction distance between the field and the sample. In this case, the molecule cannot be approximated as isolated. We have also shown the extend to which the time evolution of the degree of orientation can be shaped. Optimal control techniques were used to design the THz field which allows to reach the corresponding dynamics…

Optimal control of inhomogeneous spin ensembles : applications in NMR and quantum optics

2018

The goal of this thesis is to apply optimal control theory to the dynamics ofinhomogeneous spin ensembles. The first part focuses on the control of a spin ensemble coupled to a cavity. The theory is introduced in detail, and a general method to efficiently control spins ispresented. Several pulses are derived in the bad/good cavity regimes using numerical optimal control techniques. Additionally, non-linear generalized functions are used in order to derivesimple approximated solutions. In a second step, the problem of spin echo Signal to Noise Ratio maximization is investigated, and maximization conditions are derived. It is shown that new pulses are superior to state-of-the-art square puls…

Absorption, fluorescence and EIT processes in the extremely thin cell filled with Rb and buffer gas neon

2008

International audience; Comparison of the absorption and fluorescence in the nanocell (or so called extremely thin cell) filled with pure Rb with another one filled with Rb and Neon gas is provided. The effect of the collapse and revival of Dicke-type narrowing is still observable for thickness L=lambda/2, and lambda, where lambda , is a resonant laser wavelength either 780 nm, or 795 nm (for Rb, D2 or D1 line). For L=  so called velocity selective optical pumping (VSOP) resonance located at the atomic transition is still observable, while the linewidth is increased by 4 times in comparison with that obtained in the pure Rb nanocell. Comparison with the theory is presented. Electromagnetic…