51 research outputs found
Strong excitation of emitters in an impedance matched cavity: the area theorem, \pi-pulse and self-induced transparency
I theoretically study the behavior of strong pulses exciting emitters inside
a cavity. The ensemble is supposed to be inhomogeneously broadened and the
cavity matched finding application in quantum storage of optical or RF photons.
My analysis is based on energy and pulse area conservation rules predicting
important distortions for specific areas. It is well supported by numerical
simulations. I propose a qualitative interpretation in terms of slow-light. The
analogy with the free space situation is remarkable
Light-shift modulated photon-echo
We show that the AC-Stark shift (light-shift) is a powerful and versatile
tool to control the emission of a photon-echo in the context of optical
storage. As a proof-of-principle, we demonstrate that the photon-echo
efficiency can be fully modulated by applying light-shift control pulses in an
erbium doped solid. The control of the echo emission is attributed to the
spatial gradient induced by the light-shift beam
Phase space density limitation in laser cooling without spontaneous emission
We study the possibility to enhance the phase space density of
non-interacting particles submitted to a classical laser field without
spontaneous emission. We clearly state that, when no spontaneous emission is
present, a quantum description of the atomic motion is more reliable than
semi-classical description which can lead to large errors especially if no care
is taken to smooth structures smaller than the Heisenberg uncertainty
principle. Whatever the definition of position - momentum phase space density,
its gain is severely bounded especially when started from a thermal sample.
More precisely, the maximum phase space density, can only be improved by a
factor M for M-level atoms. This bound comes from a transfer between the
external and internal degrees of freedom. To circumvent this limit, one can use
non-coherent light fields, informational feedback cooling schemes, involve
collectives states between fields and atoms, or allow a single spontaneous
emission evenComment: 3 figures, 4 page
Piezospectroscopic measurement of high-frequency vibrations in a pulse-tube cryostat
Vibrations in cryocoolers are a recurrent concern to the end user. They
appear in different parts of the acoustic spectrum depending on the
refrigerator type, Gifford McMahon or pulse-tube, and with a variable coupling
strength to the physical system under interest. Here, we use the
piezospectroscopic effect in rare-earth doped crystals at low temperature as a
high resolution, contact-less probe for the vibrations. With this optical
spectroscopic technique, we obtain and analyze the vibration spectrum up to
700kHz of a 2kW pulse-tube cooler. We attempt an absolute calibration based on
known experimental parameters to make our method partially quantitative and to
provide a possible comparison with other well-established techniques
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
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
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
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