8,581 research outputs found
Split-sideband spectroscopy in slowly modulated optomechanics
Optomechanical coupling between the motion of a mechanical oscillator and a
cavity represents a new arena for experimental investigation of quantum effects
on the mesoscopic and macroscopic scale.The motional sidebands of the output of
a cavity offer ultra-sensitive probes of the dynamics. We introduce a scheme
whereby these sidebands split asymmetrically and show how they may be used as
experimental diagnostics and signatures of quantum noise limited dynamics. We
show split-sidebands with controllable asymmetry occur by simultaneously
modulating the light-mechanical coupling and - slowly and out
of-phase. Such modulations are generic but already occur in optically trapped
set-ups where the equilibrium point of the oscillator is varied cyclically. We
analyse recently observed, but overlooked, experimental split-sideband
asymmetries; although not yet in the quantum regime, the data suggests that
split sideband structures are easily accessible to future experiments
Cavity cooling a single charged nanoparticle
The development of laser cooling coupled with the ability to trap atoms and
ions in electromagnetic fields, has revolutionised atomic and optical physics,
leading to the development of atomic clocks, high-resolution spectroscopy and
applications in quantum simulation and processing. However, complex systems,
such as large molecules and nanoparticles, lack the simple internal resonances
required for laser cooling. Here we report on a hybrid scheme that uses the
external resonance of an optical cavity, combined with radio frequency (RF)
fields, to trap and cool a single charged nanoparticle. An RF Paul trap allows
confinement in vacuum, avoiding instabilities that arise from optical fields
alone, and crucially actively participates in the cooling process. This system
offers great promise for cooling and trapping a wide range of complex charged
particles with applications in precision force sensing, mass spectrometry,
exploration of quantum mechanics at large mass scales and the possibility of
creating large quantum superpositions.Comment: 8 pages, 5 figures Updated version includes additional references,
new title, and supplementary information include
Fractional -scaling for quantum kicked rotors without cantori
Previous studies of quantum delta-kicked rotors have found momentum
probability distributions with a typical width (localization length )
characterized by fractional -scaling, ie in regimes
and phase-space regions close to `golden-ratio' cantori. In contrast, in
typical chaotic regimes, the scaling is integer, . Here we
consider a generic variant of the kicked rotor, the random-pair-kicked particle
(RP-KP), obtained by randomizing the phases every second kick; it has no KAM
mixed phase-space structures, like golden-ratio cantori, at all. Our unexpected
finding is that, over comparable phase-space regions, it also has fractional
scaling, but . A semiclassical analysis indicates that the
scaling here is of quantum origin and is not a signature of
classical cantori.Comment: 5 pages, 4 figures, Revtex, typos removed, further analysis added,
authors adjuste
Does solar structure vary with solar magnetic activity?
We present evidence that solar structure changes with changes in solar
activity. We find that the adiabatic index, Gamma_1, changes near the second
helium ionization, i.e., at a depth of about 0.98 R_sun. We believe that this
change is a result of the change in the effective equation of state caused by
magnetic fields. Inversions should be able to detect the changes in Gamma_1 if
mode sets with reliable and precise high-degree modes are available.Comment: To appear in ApJ Letter
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