151 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
Efficiency optimization for Atomic Frequency Comb storage
We study the efficiency of the Atomic Frequency Comb storage protocol. We
show that for a given optical depth, the preparation procedure can be optimize
to significantly improve the retrieval. Our prediction is well supported by the
experimental implementation of the protocol in a \TMYAG crystal. We observe a
net gain in efficiency from 10% to 17% by applying the optimized preparation
procedure. In the perspective of high bandwidth storage, we investigate the
protocol under different magnetic fields. We analyze the effect of the Zeeman
and superhyperfine interaction
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
Optical study of the anisotropic erbium spin flip-flop dynamics
We investigate the erbium flip-flop dynamics as a limiting factor of the
electron spin lifetime and more generally as an indirect source of decoherence
in rare-earth doped insulators. Despite the random isotropic arrangement of
dopants in the host crystal, the dipolar interaction strongly depends on the
magnetic field orientation following the strong anisotropy of the -factor.
In Er:YSiO, we observe by transient optical spectroscopy a three
orders of magnitude variation of the erbium flip-flop rate (10ppm dopant
concentration). The measurements in two different samples, with 10ppm and 50ppm
concentrations, are well-supported by our analytic modeling of the dipolar
coupling between identical spins with an anisotropic -tensor. The model can
be applied to other rare-earth doped materials. We extrapolate the calculation
to Er:CaWO, Er:LiNbO and Nd:YSiO at
different concentrations
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
Optical measurement of heteronuclear cross-relaxation interactions in Tm:YAG
We investigate cross-relaxation interactions between Tm and Al in Tm:YAG
using two optical methods: spectral holeburning and stimulated echoes. These
interactions lead to a reduction in the hyperfine lifetime at magnetic fields
that bring the Tm hyperfine transition into resonance with an Al transition. We
develop models for measured echo decay curves and holeburning spectra near a
resonance, which are used to show that the Tm-Al interaction has a resonance
width of 10~kHz and reduces the hyperfine lifetime to 0.5 ms. The antihole
structure is consistent with an interaction dominated by the Al nearest
neighbors at 3.0 Angstroms, with some contribution from the next nearest
neighbors at 3.6 Angstroms.Comment: 13 pages, 9 figure
Phase-locking of two self-seeded tapered amplifier lasers
We report on the phase-locking of two diode lasers based on self-seeded
tapered amplifiers. In these lasers, a reduction of linewidth is achieved using
narrow-band high-transmission interference filters for frequency selection. The
lasers combine a compact design with a Lorentzian linewidth below 200 kHz at an
output power of 300 mW. We characterize the phase noise of the phase-locked
laser system and study its potential for coherent beam-splitting in atom
interferometers.Comment: 7 pages, 4 figure
Rephasing processes and quantum memory for light: reversibility issues and how to fix them
Time reversibility is absent from some recently proposed quantum memory
protocols such as Absorption Frequency Comb (AFC). Focusing on AFC memory, we
show that quantum efficiency and fidelity are reduced dramatically, as a
consequence of non-reversibility, when the spectral width of the incoming
signal approaches the memory bandwidth. Non-reversibility is revealed through
spectral dispersion, giving rise to phase mismatching. We propose a modified
AFC scheme that restores reversibility. This way, signals can be retrieved with
excellent efficiency over the entire memory bandwidth. This study could be
extended to other quantum memory rephasing schemes in inhomogeneously broadened
absorbing media.Comment: 8 pages, 6 figures, was presented in 20th International Laser Physics
Workshop (LPHYS'11), July 11-15, 2011, Sarajevo, Bosnia and Herzegovin
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