S. R. de Echaniz

Polarization-based light-atom quantum interface with an all-optical trap

We describe the implementation of a system for studying light-matter interactions using an ensemble of

Resonant and off-resonant transients in electromagnetically induced transparency: Turn-on and turn-off dynamics

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Observations of a doubly driven V system probed to a fourth level in laser-cooled rubidium

cold rubidium 87 atoms, trapped in a single-beam optical dipole trap. In this configuration the elongated shape of the atomic cloud increases the strength of the collective light-atom coupling. Trapping all-optically allows for long storage times in a low decoherence environment. We are able to perform several thousands of measurements on one atomic ensemble with little destruction. We report results on paramagnetic Faraday rotations from a macroscopically polarized atomic ensemble. Our results confirm that strong light-atom coupling is achievable in this system which makes it attractive for single-pass quantum information protocols.

Observation of transient gain without population inversion in a laser-cooled rubidium Lambda system

This paper presents a wide-ranging theoretical and experimental study of nonadiabatic transient phenomena in a L electromagnetically induced transparency system when a strong coupling field is rapidly switched on or off. The theoretical treatment uses a Laplace transform approach to solve the time-dependent density matrix equation. The experiments are carried out in a 87 Rb magneto-optical trap. The results show transient probe gain in parameter regions not previously studied, and provide insight into the transition dynamics between bare and dressed states.

Hamiltonian design in atom-light interactions with rubidium ensembles: A quantum-information toolbox

Observations of a doubly driven V system probed to a fourth level in an N configuration are reported. A dressed-state analysis is also presented. The expected three-peak spectrum is explored in a cold rubidium sample in a magneto-optic trap. Good agreement is found between the dressed-state theory and the experimental spectra once light shifts and uncoupled absorptions in the rubidium system are taken into account.

Diffraction effects on light-atomic-ensemble quantum interface

We have observed clear Rabi oscillations of a weak probe in a strongly driven three-level

Improvement of laser cooling of ions in a Penning trap by use of the axialization technique

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Inhomogeneities in atom-light interfaces and spin squeezing dynamics

system in laser-cooled rubidium. When the coupling field is nonadiabatically switched on using a Pockels cell, transient probe gain without population inversion is obtained in the presence of uncoupled absorptions. Our results are supported by three-state computations.

Spin squeezing experiments in a cold ensemble of 87 Rb

We study the coupling between collective variables of atomic spin and light polarization in an ensemble of cold 87Rb probed with polarized light. The effects of multiple hyperfine levels manifest themselves as a rank-2 tensor polarizability, whose irreducible components can be selected by means of probe detuning. The D1 and D2 lines of Rb are explored and we identify different detunings which lead to Hamiltonians with different symmetries for rotations. As possible applications of these Hamiltonians, we describe schemes for spin squeezing, quantum cloning, quantum memory, and measuring atom number.

Cold 87 Rb ensembles: non-Gaussian state detection and spin tomography

We present a simple method to include the effects of diffraction into the description of a light-atomic ensemble quantum interface in the context of collective variables. Carrying out a scattering calculation we single out the purely geometrical effect and apply our method to the experimental relevant case of Gaussian-shaped atomic samples stored in single beam optical dipole traps probed by a Gaussian beam. We derive simple scaling relations for the effect of the interaction geometry and compare our findings to the results from one-dimensional models of light propagation.