244 research outputs found
Microwave-stimulated Raman adiabatic passage in a Bose-Einstein condensate on an atom chip
We report the achievement of stimulated Raman adiabatic passage (STIRAP) in
the microwave frequency range between internal states of a Bose-Einstein
condensate (BEC) magnetically trapped in the vicinity of an atom chip. The
STIRAP protocol used in this experiment is robust to external perturbations as
it is an adiabatic transfer, and power-efficient as it involves only resonant
(or quasi-resonant) processes. Taking into account the effect of losses and
collisions in a non-linear Bloch equations model, we show that the maximum
transfer efficiency is obtained for non-zero values of the one- and two-photon
detunings, which is confirmed quantitatively by our experimental measurements
Orientation of Nd dipoles in yttrium aluminum garnet: A simple yet accurate model
We report an experimental study of the 1064nm transition dipoles in neodymium
doped yttrium aluminum garnet (Nd-YAG) by measuring the coupling constant
between two orthogonal modes of a laser cavity for different cuts of the YAG
gain crystal. We propose a theoretical model in which the transition dipoles,
slightly elliptic, are oriented along the crystallographic axes. Our
experimental measurements show a very good quantitative agreement with this
model, and predict a dipole ellipticity between 2% and 3%. This work provides
an experimental evidence for the simple description in which transition dipoles
and crystallographic axes are collinear in Nd-YAG (with an accuracy better than
1 deg), a point that has been discussed for years.Comment: Accepted for publication in Physical Review
A Test Resonator for Kagome Hollow-Core Photonic Crystal Fibers for Resonant Rotation Sensing
We build ring resonators to assess the potentialities of Kagome Hollow-Core
Photonic Crystal Fibers for future applications to resonant rotation sensing.
The large mode diameter of Kagome fibers permits to reduce the free space
fiber-to-fiber coupling losses, leading to cavities with finesses of about 30
for a diameter equal to 15 cm. Resonance linewidths of 3.2~MHz with contrasts
as large as 89\% are obtained. Comparison with 7-cell photonic band gap (PBG)
fiber leads to better finesse and contrast with Kagome fiber. Resonators based
on such fibers are compatible with the angular random walk required for medium
to high performance rotation sensing. The small amount of light propagating in
silica should also permit to further reduce the Kerr-induced non-reciprocity by
at least three orders of magnitudes in 7-cell Kagome fiber compared with 7-cell
PBG fiber
Experimental demonstration of a dual-frequency laser free from anti-phase noise
A reduction of more than 20 dB of the intensity noise at the anti-phase
relaxation oscillation frequency is experimentally demonstrated in a
two-polarization dual-frequency solid-state laser without any optical or
electronic feedback loop. Such a behavior is inherently obtained by aligning
the two orthogonally polarized oscillating modes with the crystallographic axes
of a (100)-cut neodymium-doped yttrium aluminum garnet active medium. The
anti-phase noise level is shown to increase as soon as one departs from this
peculiar configuration, evidencing the predominant role of the nonlinear
coupling constant. This experimental demonstration opens new perspectives on
the design and realization of extremely low noise dual-frequency solid-state
lasers
Experimental study of the role of trap symmetry in an atom-chip interferometer above the Bose-Einstein condensation threshold
We report the experimental study of an atom-chip interferometer using
ultracold rubidium 87 atoms above the Bose-Einstein condensation threshold. The
observed dependence of the contrast decay time with temperature and with the
degree of symmetry of the traps during the interferometer sequence is in good
agreement with theoretical predictions published in [Dupont-Nivet et al., NJP
18, 113012 (2016)]. These results pave the way for precision measurements with
trapped thermal atoms.Comment: 11 pages, 4 figure
Probing many-body dynamics on a 51-atom quantum simulator
Controllable, coherent many-body systems can provide insights into the
fundamental properties of quantum matter, enable the realization of new quantum
phases and could ultimately lead to computational systems that outperform
existing computers based on classical approaches. Here we demonstrate a method
for creating controlled many-body quantum matter that combines
deterministically prepared, reconfigurable arrays of individually trapped cold
atoms with strong, coherent interactions enabled by excitation to Rydberg
states. We realize a programmable Ising-type quantum spin model with tunable
interactions and system sizes of up to 51 qubits. Within this model, we observe
phase transitions into spatially ordered states that break various discrete
symmetries, verify the high-fidelity preparation of these states and
investigate the dynamics across the phase transition in large arrays of atoms.
In particular, we observe robust manybody dynamics corresponding to persistent
oscillations of the order after a rapid quantum quench that results from a
sudden transition across the phase boundary. Our method provides a way of
exploring many-body phenomena on a programmable quantum simulator and could
enable realizations of new quantum algorithms.Comment: 17 pages, 13 figure
Mode coupling control in a resonant device: application to solid-state ring lasers
A theoretical and experimental investigation of the effects of mode coupling
in a resonant macro- scopic quantum device is achieved in the case of a ring
laser. In particular, we show both analytically and experimentally that such a
device can be used as a rotation sensor provided the effects of mode coupling
are controlled, for example through the use of an additional coupling. A
possible general- ization of this example to the case of another resonant
macroscopic quantum device is discussed
Spectral Engineering of Cavity-Protected Polaritons in an Atomic Ensemble with Controlled Disorder
The paradigm of quantum emitters coupled to a single cavity mode appears
in many situations ranging from quantum technologies to polaritonic chemistry.
The ideal case of identical emitters is elegantly modeled in terms of symmetric
states, and understood in terms of polaritons. In the practically relevant case
of an inhomogeneous frequency distribution, this simple picture breaks down and
new and surprising features appear. Here we leverage the high degree of control
in a strongly coupled cold atom system, where for the first time the ratio
between coupling strength and frequency inhomogeneities can be tuned. We
directly observe the transition from a disordered regime to a polaritonic one
with only two resonances. The latter are much narrower than the frequency
distribution, as predicted in the context of ''cavity protection''. We find
that the concentration of the photonic weight of the coupled light-matter
states is a key parameter for this transition, and demonstrate that a simple
parameter based on statistics of transmission count spectra provides a robust
experimental proxy for this theoretical quantity. Moreover, we realize a
dynamically modulated Tavis-Cumming model to produce a comb of narrow polariton
resonances protected from the disorder, with potential applications to quantum
networks
Quantum Kibble-Zurek mechanism and critical dynamics on a programmable Rydberg simulator
Quantum phase transitions (QPTs) involve transformations between different
states of matter that are driven by quantum fluctuations. These fluctuations
play a dominant role in the quantum critical region surrounding the transition
point, where the dynamics are governed by the universal properties associated
with the QPT. While time-dependent phenomena associated with classical,
thermally driven phase transitions have been extensively studied in systems
ranging from the early universe to Bose Einstein Condensates, understanding
critical real-time dynamics in isolated, non-equilibrium quantum systems is an
outstanding challenge. Here, we use a Rydberg atom quantum simulator with
programmable interactions to study the quantum critical dynamics associated
with several distinct QPTs. By studying the growth of spatial correlations
while crossing the QPT, we experimentally verify the quantum Kibble-Zurek
mechanism (QKZM) for an Ising-type QPT, explore scaling universality, and
observe corrections beyond QKZM predictions. This approach is subsequently used
to measure the critical exponents associated with chiral clock models,
providing new insights into exotic systems that have not been understood
previously, and opening the door for precision studies of critical phenomena,
simulations of lattice gauge theories and applications to quantum optimization
- …