51 research outputs found
Spin-Cooling of the Motion of a Trapped Diamond
Observing and controlling macroscopic quantum systems has long been a driving
force in research on quantum physics. In this endeavor, strong coupling between
individual quantum systems and mechanical oscillators is being actively
pursued. While both read-out of mechanical motion using coherent control of
spin systems and single spin read-out using pristine oscillators have been
demonstrated, temperature control of the motion of a macroscopic object using
long-lived electronic spins has not been reported. Here, we observe both a
spin-dependent torque and spin-cooling of the motion of a trapped microdiamond.
Using a combination of microwave and laser excitation enables the spin of
nitrogen-vacancy centers to act on the diamond orientation and to cool the
diamond libration via a dynamical back-action. Further, driving the system in
the non-linear regime, we demonstrate bistability and self-sustained coherent
oscillations stimulated by the spin-mechanical coupling, which offers prospects
for spin-driven generation of non-classical states of motion. Such a levitating
diamond operated as a compass with controlled dissipation has implications in
high-precision torque sensing, emulation of the spin-boson problem and probing
of quantum phase transitions. In the single spin limit and employing ultra-pure
nano-diamonds, it will allow quantum non-demolition read-out of the spin of
nitrogen-vacancy centers under ambient conditions, deterministic entanglement
between distant individual spins and matter-wave interferometry.Comment: New version with a calibration of angular resolution and sensitivity.
Fig. 1 is also replaced to show an ODMR when the diamond is static to avoid
spin-torque induced distortion
Spin-mechanics with levitating ferromagnetic particles
We propose and demonstrate first steps towards schemes where the librational
mode of levitating ferromagnets is strongly coupled to the electronic spin of
Nitrogen-Vacancy (NV) centers in diamond. Experimentally, we levitate
ferromagnets in a Paul trap and employ magnetic fields to attain oscillation
frequencies in the hundreds of kHz range with Q factors close to . These
librational frequencies largely exceed the decoherence rate of NV centers in
typical CVD grown diamonds offering prospects for sideband resolved operation.
We also prepare and levitate composite diamond-ferromagnet particles and
demonstrate both coherent spin control of the NV centers and read-out of the
particle libration using the NV spin. Our results will find applications in
ultra-sensitive gyroscopy and bring levitating objects a step closer to
spin-mechanical experiments at the quantum level.Comment: Lengthened to 11 pages. To appear in PR
Full counting statistics and phase diagram of a dissipative Rydberg gas
Ultra-cold gases excited to strongly interacting Rydberg states are a
promising system for quantum simulations of many-body systems. For off-resonant
excitation of such systems in the dissipative regime, highly correlated
many-body states exhibiting, among other characteristics, intermittency and
multi-modal counting distributions are expected to be created. So far,
experiments with Rydberg atoms have been carried out in the resonant,
non-dissipative regime. Here we realize a dissipative gas of rubidium Rydberg
atoms and measure its full counting statistics for both resonant and
off-resonant excitation. We find strongly bimodal counting distributions in the
off-resonant regime that are compatible with intermittency due to the
coexistence of dynamical phases. Moreover, we measure the phase diagram of the
system and find good agreement with recent theoretical predictions. Our results
pave the way towards detailed studies of many-body effects in Rydberg gases.Comment: 12 pages, 5 figure
Observation of a resonant four-body interaction in cold cesium Rydberg atoms
Cold Rydberg atoms subject to long-range dipole-dipole interactions represent
a particularly interesting system for exploring few-body interactions and
probing the transition from 2-body physics to the many-body regime. In this
work we report the direct observation of a resonant 4-body Rydberg interaction.
We exploit the occurrence of an accidental quasi-coincidence of a 2-body and a
4-body resonant Stark-tuned Forster process in cesium to observe a resonant
energy transfer requiring the simultaneous interaction of at least four
neighboring atoms. These results are relevant for the implementation of quantum
gates with Rydberg atoms and for further studies of many-body physics.Comment: 5 pages, 5 figure
Magnetic-Torque Enhanced by Tunable Dipolar interactions
We use tunable dipolar-interactions between the spins of nitrogen-vacancy
(NV) centers in diamond to rotate a diamond crystal. Specifically, we employ
cross-relaxation between the electronic spin of pairs of NV centers in a
trapped diamond to enhance the anisotropic NV paramagnetism and thus to
increase the associated spin torque. Our observations open a path towards the
use of mechanical oscillators to detect paramagnetic defects that lack optical
transitions, to investigation of angular momentum conservation in spin
relaxation processes and to novel means of cooling the motion of mechanical
oscillators.Comment: 15 page
Optical Detection of Paramagnetic Defects in a CVD-grown Diamond
The electronic spins of the nitrogen-vacancy centers (NV centers) in
Chemical-Vapor-Deposition (CVD) grown diamonds form ideal probes of magnetic
fields and temperature, as well as promising qu-bits for quantum information
processing. Studying and controlling the magnetic environment of NV centers in
such high purity crystals is thus essential for these applications. We
demonstrate optical detection of paramagnetic species, such as hydrogen-related
complexes, in a CVD-grown diamond. The resonant transfer of the NV centers'
polarized electronic spins to the electronic spins of these species generates
conspicuous features in the NV photoluminescence by employing magnetic field
scans along the [100] crystal direction. Our results offer prospects for more
detailed studies of CVD-grown processes as well as for coherent control of the
spin of novel classes of hyper-polarized paramagnetic species.Comment: 8 pages including appendi
Rydberg electrometry for optical lattice clocks
Electrometry is performed using Rydberg states to evaluate the quadratic Stark shift of the 5s2 1 S0-5s5p 3 P0 clock transition in strontium. By measuring the Stark shift of the highly excited 5s75d 1 D2 state using electromagnetically induced transparency, we characterize the electric field with sufficient precision to provide tight constraints on the systematic shift to the clock transition. Using the theoretically derived, and experimentally verified, polarizability for this Rydberg state, we can measure the residual field with an uncertainty well below 1Vmâ1. This resolution allows us to constrain the fractional frequency uncertainty of the quadratic Stark shift of the clock transition to 2Ă10â20
Proposition d'un indice de synchronisation pour la validation de modÚles de réponses neuronales à des stimuli périodiques
Il est courant d'Ă©valuer le degrĂ© de synchronisation d'une rĂ©ponse neuronale Ă un stimulus pĂ©riodique pour la caractĂ©riser. En neurophysiologie et par consĂ©quent en modĂ©lisation, la mesure du vecteur dominant de Goldberg et Brown (1969) est trĂšs rĂ©pandue. Les dĂ©fauts de cet indice sont explicitĂ©s et un nouvel indice les corrigeant est proposĂ©. Une base de tests est construite pour Ă©valuer le comportement de ceux-ci dans diffĂ©rentes situations. Il apparaĂźt d'une part que l'interprĂ©tation en termes de synchronisation de l'indice vecteur dominant doit ĂȘtre faite avec prĂ©caution, et d'autre part que le nouvel indice est une mesure qui, Ă elle seule, permet de mieux rendre compte de la synchronisation d'une rĂ©ponse neuronale. Cet indice est paramĂ©trable, ce qui offre un certain Ă©ventail de comportements
- âŠ