840 research outputs found
Endoscopic imaging of quantum gases through a fiber bundle
We use a coherent fiber bundle to demonstrate the endoscopic absorption
imaging of quantum gases. We show that the fiber bundle introduces spurious
noise in the picture mainly due to the strong core-to-core coupling. By direct
comparison with free-space pictures, we observe that there is a maximum column
density that can be reliably measured using our fiber bundle, and we derive a
simple criterion to estimate it. We demonstrate that taking care of not
exceeding such maximum, we can retrieve exact quantitative information about
the atomic system, making this technique appealing for systems requiring
isolation form the environment
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Manipulation and control of ultra-cold rubidium atoms
During the course of this PhD an experimental set-up has been designed and implemented to confine neutral atoms in microscopic dipole traps and to manipulate their internal states by laser excitation to Rydberg states. A lot of effort was devoted to the stabilization of the laser sources for two-photon excitation to the Rydberg states, using techniques based on modulation transfer spectroscopy and electromagnetically induced transparency (EIT). Taking advantage of the EIT spectroscopy scheme, we have measured for the first time the electric dipole moments for the transitions between the first excited 5P3/2 and Rydberg nDS/2 level of rubidium. These measurements provided benchmarking of existing theoretical models to calculate the reduced matrix elements and have helped us to identify the D'yachkov Pankratov method as a particularly reliable one. Therefore we made use of the existing code to calculate the relative radial matrix elements for bound-bound, bound-free and free-free transitions between arbitrary states of alkali atoms. Our results allowed us to identify many features of interest and several Cooper minima have been revealed for the first time. The preparation of a new apparatus required ultra-high vacuum for efficient laser cooling and trapping experiments. A unique 4-beam magneto-optical trap has been designed and implemented in our new system. The tetrahedral MOT operating at a very acute beams angle has been demonstrated for the first time. The characterisation of the basic properties of our MOT has highlighted. some interesting new cooling mechanisms that do not fully match existing theoretical models and will require further investigation. It has been demonstrated that our tetrahedral MOT is suitable to prepare cold, diluted reservoirs of atoms and therefore efficiently load our microscopic dipole trap
Exploring the thermodynamics of spin-1 Rb Bose Gases with synthetic magnetization
In this work, we study the thermodynamic properties of a spin-1 Bose gas
across the Bose-Einstein condensation transition. We present the theoretical
description of the thermodynamics of a trapped ideal spin-1 Bose gas and we
describe the phases that can be obtained in this system as a function of the
temperature and of the populations in the different spin components. We propose
a simple way to realize a "synthetic magnetization" that can be used to probe
the entire phase diagram while keeping the real magnetization of the system
fixed. We experimentally demonstrate the use of such method to explore
different phases in a sample with zero total magnetization. Our work opens up
new perspectives to study isothermal quenching dynamics through different
magnetic phases in spinor condensates
Vortex conveyor belt for matter-wave coherent splitting and interferometry
We numerically study a matter wave interferometer realized by splitting a
trapped Bose-Einstein condensate with phase imprinting. We show that a simple
step-like imprinting pattern rapidly decays into a string of vortices that can
generate opposite velocities on the two halves of the condensate. We first
study in detail the splitting and launching effect of these vortex structures,
whose functioning resembles the one of a conveyor belt, and we show that the
initial exit velocity along the vortex conveyor belt can be controlled
continuously by adjusting the vortex distance. We finally characterize the
complete interferometric sequence, demonstrating how the phase of the resulting
interference fringe can be used to measure an external acceleration. The
proposed scheme has the potential to be developed into compact and high
precision accelerometers
Health policy in the Polish health care system
The main goal of health policy is to ensure the health security of society. There are many
definitions of health policy. Health policy is one of the most important forms of public
activity. Health policy programs include multi-annual programs established by the Council of
Ministers. They implement the strategies adopted by the government - they concern important
phenomena and problems that require decisions and actions at the level of the Council of
Ministers. As part of social policy, it should be embedded in social and economic realities and
be oriented on ensuring conditions favorable to maintaining the health of societies
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