845 research outputs found
Optomechanics
We review recent progress in the field of optomechanics, where one studies
the effects of radiation on mechanical motion. The paradigmatic example is an
optical cavity with a movable mirror, where the radiation pressure can induce
cooling, amplification and nonlinear dynamics of the mirror.Comment: 12 pages, 4 figures, submitted to the proceedings of the NATO
Advanced Research Workshop 'Recent Advances in Nonlinear Dynamics and Complex
System Physics', Tashkent, Uzbekistan, 200
Entanglement of mechanical oscillators coupled to a non-equilibrium environment
Recent experiments aim at cooling nanomechanical resonators to the ground
state by coupling them to non-equilibrium environments in order to observe
quantum effects such as entanglement. This raises the general question of how
such environments affect entanglement. Here we show that there is an optimal
dissipation strength for which the entanglement between two coupled oscillators
is maximized. Our results are established with the help of a general framework
of exact quantum Langevin equations valid for arbitrary bath spectra, in and
out of equilibrium. We point out why the commonly employed Lindblad approach
fails to give even a qualitatively correct picture
Multistability and spin diffusion enhanced lifetimes in dynamic nuclear polarization in a double quantum dot
The control of nuclear spins in quantum dots is essential to explore their
many-body dynamics and exploit their prospects for quantum information
processing. We present a unique combination of dynamic nuclear spin
polarization and electric-dipole-induced spin resonance in an electrostatically
defined double quantum dot (DQD) exposed to the strongly inhomogeneous field of
two on-chip nanomagnets. Our experiments provide direct and unrivaled access to
the nuclear spin polarization distribution and allow us to establish and
characterize multiple fixed points. Further, we demonstrate polarization of the
DQD environment by nuclear spin diffusion which significantly stabilizes the
nuclear spins inside the DQD
Full photon statistics of a light beam transmitted through an optomechanical system
In this paper, we study the full statistics of photons transmitted through an
optical cavity coupled to nanomechanical motion. We analyze the entire temporal
evolution of the photon correlations, the Fano factor, and the effects of
strong laser driving, all of which show pronounced features connected to the
mechanical backaction. In the regime of single-photon strong coupling, this
allows us to predict a transition from sub-Poissonian to super-Poissonian
statistics for larger observation time intervals. Furthermore, we predict
cascades of transmitted photons triggered by multi-photon transitions. In this
regime, we observe Fano factors that are drastically enhanced due to the
mechanical motion.Comment: 8 pages, 7 figure
Enhanced quantum nonlinearities in a two mode optomechanical system
In cavity optomechanics, nanomechanical motion couples to a localized optical
mode. The regime of single-photon strong coupling is reached when the optical
shift induced by a single phonon becomes comparable to the cavity linewidth. We
consider a setup in this regime comprising two optical modes and one mechanical
mode. For mechanical frequencies nearly resonant to the optical level
splitting, we find the photon-phonon and the photon-photon interactions to be
significantly enhanced. In addition to dispersive phonon detection in a novel
regime, this offers the prospect of optomechanical photon measurement. We study
these QND detection processes using both analytical and numerical approaches
The optomechanical instability in the quantum regime
We consider a generic optomechanical system, consisting of a driven optical
cavity and a movable mirror attached to a cantilever. Systems of this kind (and
analogues) have been realized in many recent experiments. It is well known that
those systems can exhibit an instability towards a regime where the cantilever
settles into self-sustained oscillations. In this paper, we briefly review the
classical theory of the optomechanical instability, and then discuss the
features arising in the quantum regime. We solve numerically a full quantum
master equation for the coupled system, and use it to analyze the photon
number, the cantilever's mechanical energy, the phonon probability distribution
and the mechanical Wigner density, as a function of experimentally accessible
control parameters. We observe and discuss the quantum-to-classical transition
as a function of a suitable dimensionless quantum parameter.Comment: 23 pages, 6 figures, subm. to focus issue of New Journal of Physics
on "Mechanical Systems at the Quantum Limit
Self-induced oscillations in an optomechanical system
We have explored the nonlinear dynamics of an optomechanical system
consisting of an illuminated Fabry-Perot cavity, one of whose end-mirrors is
attached to a vibrating cantilever. Such a system can experience negative
light-induced damping and enter a regime of self-induced oscillations. We
present a systematic experimental and theoretical study of the ensuing
attractor diagram describing the nonlinear dynamics, in an experimental setup
where the oscillation amplitude becomes large, and the mirror motion is
influenced by several optical modes. A theory has been developed that yields
detailed quantitative agreement with experimental results. This includes the
observation of a regime where two mechanical modes of the cantilever are
excited simultaneously.Comment: 4.5 pages, 3 figures (v2: corrected few typos
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