33 research outputs found
Photon echoes in strongly scattering media: a diagrammatic approach
We study photon echo generation in disordered media with the help of multiple
scattering theory based on diagrammatic approach and numerical simulations. We
show that a strong correlation exists between the driving fields at the origin
of the echo and the echo beam. Opening the way to a better understanding of
non-linear wave propagation in complex materials, this work supports recent
experimental results with applications to the measurement of the optical dipole
lifetime in powders
Quantum memory for light: large efficiency at telecom wavelength
We implement the ROSE protocol in an erbium doped solid, compatible with the
telecom range. The ROSE scheme is an adaptation of the standard 2-pulse photon
echo to make it suitable for a quantum memory. We observe an efficiency of 40%
in a forward direction by using specific orientations of the light
polarizations, magnetic field and crystal axes
Selective optical addressing of nuclear spins through superhyperfine interaction in rare-earth doped solids
In Er:YSiO, we demonstrate the selective optical addressing of
the Y nuclear spins through their superhyperfine coupling with
the Er electronic spins possessing large Land\'e -factors. We
experimentally probe the electron-nuclear spin mixing with photon echo
techniques and validate our model. The site-selective optical addressing of the
Y nuclear spins is designed by adjusting the magnetic field strength and
orientation. This constitutes an important step towards the realization of
long-lived solid-state qubits optically addressed by telecom photons.Comment: 5 pages, 4 figures, supplementary material (3 pages
Securing coherence rephasing with a pair of adiabatic rapid passages
Coherence rephasing is an essential step in quantum storage protocols that
use echo-based strategies. We present a thorough analysis on how two adiabatic
rapid passages (ARP) are able to rephase atomic coherences in an
inhomogeneously broadened ensemble. We consider both the cases of optical and
spin coherences, rephased by optical or radio-frequency (rf) ARPs,
respectively. We show how a rephasing sequence consisting of two ARPs in a
double-echo scheme is equivalent to the identity operator (any state can be
recovered), as long as certain conditions are fulfilled. Our mathematical
treatment of the ARPs leads to a very simple geometrical interpretation within
the Bloch sphere that permits a visual comprehension of the rephasing process.
We also identify the conditions that ensure the rephasing, finding that the
phase of the optical or rf ARP fields plays a key role in the capability of the
sequence to preserve the phase of the superposition state. This settles a
difference between optical and rf ARPs, since field phase control is not
readily guaranteed in the former case. We also provide a quantitative
comparison between -pulse and ARP rephasing efficiencies, showing the
superiority of the latter. We experimentally verify the conclusions of our
analysis through rf ARP rephasing sequencies performed on the rare-earth
ion-doped crystal Tm:YAG, of interest in quantum memories.Comment: 24 pages, 7 figure
Interlaced spin grating for optical wave filtering
Interlaced Spin Grating is a scheme for the preparation of spectro-spatial
periodic absorption gratings in a inhomogeneously broadened absorption profile.
It relies on the optical pumping of atoms in a nearby long-lived ground state
sublevel. The scheme takes advantage of the sublevel proximity to build large
contrast gratings with unlimited bandwidth and preserved average optical depth.
It is particularly suited to Tm-doped crystals in the context of classical and
quantum signal processing. In this paper, we study the optical pumping dynamics
at play in an Interlaced Spin Grating and describe the corresponding absorption
profile shape in an optically thick atomic ensemble. We show that, in Tm:YAG,
the diffraction efficiency of such a grating can reach 18.3% in the small
angle, and 11.6% in the large angle configuration when the excitation is made
of simple pulse pairs, considerably outperforming conventional gratings.Comment: 11 pages, 13 figures in Physical Review A, 201
Optical memory bandwidth and multiplexing capacity in the erbium telecommunication window
We study the bandwidth and multiplexing capacity of an erbium-doped optical
memory for quantum storage purposes. We concentrate on the protocol ROSE
(Revival of a Silenced Echo) because it has the largest potential multiplexing
capacity. Our analysis is applicable to other protocols that involve strong
optical excitation. We show that the memory performance is limited by
instantaneous spectral diffusion and we describe how this effect can be
minimised to achieve optimal performance
Ralentir le déphasage des états de superposition atomiques dans un cristal de Tm3+ (YAG)
Ce travail se place dans le contexte des recherches sur les mémoires quantiques pour la lumière. L information quantique est stockée dans un état de superposition atomique, dont la durée de vie détermine le temps maximum de stockage.On s intéresse particulièrement aux matériaux capables de capturer la lumière par excitation résonnante d une raie d absorption, puis de conserver l information quantique dans un état de superposition du fondamental électronique.Dans Tm3+:YAG, l information est enregistrée dans un état de spin nucléaire. Cependant le champ magnétique qui lève la dégénérescence nucléaire entraîne les différents spins à des vitesses de précession différentes, ce qui tend à détruire l aimantation initiale, porteuse de l information.Une étude quantique du cristal est réalisée lors du premier chapitre de ce manuscrit. Les trois chapitres suivants traitent des différents mécanismes conduisant au déphasage des spins nucléaires. On y trouvera différente analyses théoriques qui seront confirmées par un ensemble de résultats expérimentaux, ainsi qu une description détaillée du dispositif expérimental. Enfin le dernier chapitre, prospectif, exploite les outils développés au cours de la thèse pour préserver les cohérences optiques. Il présente quelques résultats expérimentaux prometteurs sur l allongement du temps de vie de ces cohérences optiques.This work takes place in the context of research about quantum memories for light. The quantum information is stored in an atomic superposition state whose lifetime sets the maximum storage time. We are particularly interested in materials which are able to hold the light by resonant excitation of an absorption line, preserving the quantum information in a superposition state of the electronicfundamental.n Tm3+:YAG the information is stored in a nuclear spin state. However, the magnetic field which lifts the nuclear degeneracy generates different precession speeds of the spins. This destroys theinitial magnetization carrier of the information.In the first chapter of this thesis, a quantum analysis of the crystal is done. The following three chapters are devoted to different mechanisms to control the nuclear spins dephasing. There it ispossible to find different theoretical analysis which will be confirmed by a series of experimental measurements, including an extended description of the set-up. Finally, the last chapter presentsthe different techniques used to preserve the optical coherence. Promising experimental measurements are presented to extend the life time of the optical coherences.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF
Time reversal of light by linear dispersive filtering near atomic resonance
Based on the similarity of paraxial diffraction and dispersion mathematical
descriptions, the temporal imaging of optical pulses combines linear dispersive
filters and quadratic phase modulations operating as time lenses. We consider
programming a dispersive filter near atomic resonance in rare earth ion doped
crystals, which leads to unprecedented high values of dispersive power. This
filter is used in an approximate imaging scheme, combining a single time lens
and a single dispersive section and operating as a time reversing device, with
potential applications in radio-frequency signal processing. This scheme is
closely related to three-pulse photon echo with chirped pulses but the
connection with temporal imaging and dispersive filtering emphasizes new
features.Comment: 21 pages, 11 figure
Stimulated Raman adiabatic passage in Tm3+:YAG
International audienceWe report on the experimental demonstration of stimulated Raman adiabatic passage in a Tm 3+ : YAG crystal. Tm 3+ : YAG is a promising material for use in quantum information processing applications, but as yet there are few experimental investigations of coherent Raman processes in this material. We investigate the effect of inhomogeneous broadening and Rabi frequency on the transfer efficiency and the width of the two-photon spectrum. Simulations of the complete Tm 3+ : YAG system are presented along with the corresponding experimental results