2,761 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
Conception d'un injecteur de données hardware
L'expérience LHCb, menée dans le cadre du CERN, recueille un nombre extraordinaire de données. Le systÚme d'acquisition de ces données est donc démesuré, entiÚrement dédié à cette tùche. Pour réaliser des tests sur ce systÚme d'acquisition, hors expérience, il existe un injecteur de données qui permet de simuler le flot habituel. Dans l'optique d'une future optimisation du réseau de ce systÚme en Ethernet 10 gigabit, le LHCb souhaite se doter d'un injecteur hardware permettant de fonctionner sur ce nouveau réseau et d'y tester différents types de protocoles de communication tels qu'IP, MEP et TCP. Cet injecteur est réalisé au moyen d'une carte de développement Altera munie d'un FPGA et de différentes interfaces de communications
A mathematical analysis of the effects of Hebbian learning rules on the dynamics and structure of discrete-time random recurrent neural networks
We present a mathematical analysis of the effects of Hebbian learning in
random recurrent neural networks, with a generic Hebbian learning rule
including passive forgetting and different time scales for neuronal activity
and learning dynamics. Previous numerical works have reported that Hebbian
learning drives the system from chaos to a steady state through a sequence of
bifurcations. Here, we interpret these results mathematically and show that
these effects, involving a complex coupling between neuronal dynamics and
synaptic graph structure, can be analyzed using Jacobian matrices, which
introduce both a structural and a dynamical point of view on the neural network
evolution. Furthermore, we show that the sensitivity to a learned pattern is
maximal when the largest Lyapunov exponent is close to 0. We discuss how neural
networks may take advantage of this regime of high functional interest
Towards continuous-wave regime teleportation for light matter quantum relay stations
We report a teleportation experiment involving narrowband entangled photons
at 1560 nm and qubit photons at 795 nm emulated by faint laser pulses. A
nonlinear difference frequency generation stage converts the 795 nm photons to
1560 nm in order to enable interference with one photon out of the pairs, i.e.,
at the same wavelength. The spectral bandwidth of all involved photons is of
about 25 MHz, which is close to the emission bandwidth of emissive quantum
memory devices, notably those based on ensembles of cold atoms and rare earth
ions. This opens the route towards the realization of hybrid quantum nodes,
i.e., combining quantum memories and entanglement-based quantum relays
exploiting either a synchronized (pulsed) or asynchronous (continuous- wave)
scenario
Coherent Population Trapping with a controlled dissipation: applications in optical metrology
We analyze the properties of a pulsed Coherent Population Trapping protocol
that uses a controlled decay from the excited state in a -level
scheme. We study this problem analytically and numerically and find regimes
where narrow transmission, absorption, or fluorescence spectral lines occur. We
then look for optimal frequency measurements using these spectral features by
computing the Allan deviation in the presence of ground state decoherence and
show that the protocol is on a par with Ramsey-CPT. We discuss possible
implementations with ensembles of alkali atoms and single ions and demonstrate
that typical pulsed-CPT experiments that are realized on femto-second
time-scales can be implemented on micro-seconds time-scales using this scheme.Comment: 9 pages, 7 figure
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
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