309 research outputs found
Fast compression of a cold atomic cloud using a blue detuned crossed dipole trap
We present the experimental realization of a compressible blue detuned
crossed dipole trap for cold atoms allowing for fast dynamical compression (~ 5
- 10 ms) of 5x10^7 Rubidium atoms up to densities of ~ 10^13 cm^-3. The dipole
trap consists of two intersecting tubes of blue-detuned laser light. These
tubes are formed using a single, rapidly rotating laser beam which, for
sufficiently fast rotation frequencies, can be accurately described by a
quasi-static potential. The atomic cloud is compressed by dynamically reducing
the trap volume leading to densities close to the Ioffe-Reggel criterion for
light localization.Comment: 14 pages, 15 figures, 2 table
Observation of a phononic Mollow triplet in a hybrid spin-nanomechanical system
Reminiscent of the bound character of a qubit's dynamics confined on the
Bloch sphere, the observation of a Mollow triplet in the resonantly driven
qubit fluorescence spectrum represents one of the founding signatures of
Quantum Electrodynamics. Here we report on its observation in a hybrid
spin-nanomechanical system, where a Nitro-gen Vacancy spin qubit is
magnetically coupled to the vibrations of a Silicon Carbide nanowire. A
resonant microwave field turns the originally parametric hybrid interac-tion
into a resonant process, where acoustic phonons are now able to induce
transitions between the dressed qubit states, leading to synchronized
spin-oscillator dynamics. We further explore the vectorial character of the
hybrid coupling to the bidimensional de-formations of the nanowire. The
demonstrated microwave assisted synchronization of the spin-oscillator dynamics
opens novel perspectives for the exploration of spin-dependent forces, the
key-ingredient for quantum state transfer
Deviation from the normal mode expansion in a coupled graphene-nanomechanical system
We optomechanically measure the vibrations of a nanomechanical system made of
a graphene membrane suspended on a silicon nitride nanoresonator. When probing
the thermal noise of the coupled nanomechanical device, we observe a
significant deviation from the normal mode expansion. It originates from the
heterogeneous character of mechanical dissipation over the spatial extension of
coupled eigenmodes, which violates one of the fundamental prerequisite for
employing this commonly used description of the nanoresonators' thermal noise.
We subsequently measure the local mechanical susceptibility and demonstrate
that the fluctuation-dissipation theorem still holds and permits a proper
evaluation of the thermal noise of the nanomechanical system. Since it
naturally becomes delicate to ensure a good spatial homogeneity at the
nanoscale, this approach is fundamental to correctly describe the thermal noise
of nanomechanical systems which ultimately impact their sensing capacity
Nano-optomechanical measurement in the photon counting regime
Optically measuring in the photon counting regime is a recurrent challenge in
modern physics and a guarantee to develop weakly invasive probes. Here we
investigate this idea on a hybrid nano-optomechanical system composed of a
nanowire hybridized to a single Nitrogen-Vacancy (NV) defect. The vibrations of
the nanoresonator grant a spatial degree of freedom to the quantum emitter and
the photon emission event can now vary in space and time. We investigate how
the nanomotion is encoded on the detected photon statistics and explore their
spatio-temporal correlation properties. This allows a quantitative measurement
of the vibrations of the nanomechanical oscillator at unprecedentedly low light
intensities in the photon counting regime when less than one photon is detected
per oscillation period, where standard detectors are dark-noise-limited. These
results have implications for probing weakly interacting nanoresonators, for
low temperature experiments and for investigating single moving markers
First dating results for the Middle Pleistocene industries (Acheulean – Early Middle Palaeolithic) in the Pyrenees – Garonne region: a multi methods geochronological approach (TL, OSL and TT-OSL) of the Duclos and Romentères sites
The recent development work of the A65 highway has given the opportunity to broaden the corpus of Lower and Middle Palaeolithic open-air sites known in the southern Aquitaine basin. The sites of Duclos (Auriac, Pyrénées-Orientales) and Romentères (Le Vignau, Landes), discovered in this context, have yielded an abundant lithic record which has been attributed to the Acheulean of Iberian type for the earlier and, essentially, to the Early Middle Palaeolithic for the latter. The archaeological levels are intercalated in sequences that comprise aeolian silts and colluvial units separated by interglacial luvisols. The pedostratigraphic context of the two sites has provided a rare opportunity to propose a reliable chronostratigraphic framework in this area. To achieve this objective, a study combining several methods of luminescence dating was conducted to complete the geomorphological data. Optically Stimulated Luminescence (OSL) and Thermically Transferred OSL (TT-OSL) dating methods were applied in order to determine the ages of sedimentary quartz grains and thus, of the sampled deposits. In parallel, heated flint and quartzite samples were dated by thermoluminescence (TL). The Pyrenees-Garonne Acheulean industry of Duclos has been attributed to the boundary between Marine Isotopic Stages (MIS) 7 and 6 while the human occupations of Romentères date from MIS 6 for the most recent series (Early Middle Palaeolithic) and from MIS 9 and 8 for the older
Quantum-mechanics free subsystem with mechanical oscillators
Quantum mechanics sets a limit for the precision of measurement of the
position of an oscillator. The quantum noise associated with the measurement of
a quadrature of the motion imprints a backaction on the orthogonal quadrature,
which feeds back to the measured observable in the case of a continuous
measurement. In a quantum backaction evading measurement, the added noise can
be confined in the orthogonal quadrature. Here we show how it is possible to
evade this limitation and measure an oscillator without backaction by
constructing one effective oscillator from two physical oscillators. This
facilitates detection of weak forces and the creation and measurement of
nonclassical motional states of the oscillators. We realize the proposal using
two micromechanical oscillators, and show the measurements of two collective
quadratures while evading the quantum backaction by decibels on both of
them, obtaining a total noise within a factor two from the full quantum limit.
Moreover, by modifying the measurement we directly verify the quantum
entanglement of the two oscillators by measuring the Duan quantity
decibels below the separability bound
Ground-state cooling of a mechanical oscillator by heating
Dissipation and the accompanying fluctuations are often seen as detrimental
for quantum systems, since they are associated with fast relaxation and loss of
phase coherence. However, it has been proposed that a pure state can be
prepared if external noise induces suitable downwards transitions, while
exciting transitions are blocked. We demonstrate such a refrigeration mechanism
in a cavity optomechanical system, where we prepare a mechanical oscillator in
its ground state by injecting strong electromagnetic noise at frequencies
around the red mechanical sideband of the cavity. The optimum cooling is
reached with a noise bandwidth smaller than, but on the order of the cavity
decay rate. At higher bandwidths, cooling is less efficient. In the opposite
regime where the noise bandwidth becomes comparable to the mechanical damping
rate, damping follows the noise amplitude adiabatically, and the cooling is
also suppressed
The Life Cycle of Toxoplasma gondii in the Natural Environment
Chapitre 1International audienc
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