1,079 research outputs found
Time-Continuous Bell Measurements
We combine the concept of Bell measurements, in which two systems are
projected into a maximally entangled state, with the concept of continuous
measurements, which concerns the evolution of a continuously monitored quantum
system. For such time-continuous Bell measurements we derive the corresponding
stochastic Schr\"odinger equations, as well as the unconditional feedback
master equations. Our results apply to a wide range of physical systems, and
are easily adapted to describe an arbitrary number of systems and measurements.
Time-continuous Bell measurements therefore provide a versatile tool for the
control of complex quantum systems and networks. As examples we show show that
(i) two two-level systems can be deterministically entangled via homodyne
detection, tolerating photon loss up to 50%, and (ii) a quantum state of light
can be continuously teleported to a mechanical oscillator, which works under
the same conditions as are required for optomechanical ground state cooling.Comment: 4+4 pages, 4 figure
Optimal state estimation for cavity optomechanical systems
We demonstrate optimal state estimation for a cavity optomechanical system
through Kalman filtering. By taking into account nontrivial experimental noise
sources, such as colored laser noise and spurious mechanical modes, we
implement a realistic state-space model. This allows us to obtain the
conditional system state, i.e., conditioned on previous measurements, with
minimal least-square estimation error. We apply this method for estimating the
mechanical state, as well as optomechanical correlations both in the weak and
strong coupling regime. The application of the Kalman filter is an important
next step for achieving real-time optimal (classical and quantum) control of
cavity optomechanical systems.Comment: replaced with published version, 5+12 page
Quantum entanglement and teleportation in pulsed cavity-optomechanics
Entangling a mechanical oscillator with an optical mode is an enticing and
yet a very challenging goal in cavity optomechanics. Here we consider a pulsed
scheme to create Einstein-Podolsky-Rosen-type entanglement between a
traveling-wave light pulse and a mechanical oscillator. The entanglement can be
verified unambiguously by a pump-probe sequence of pulses. In contrast to
schemes that work in a steady-state regime under a continuous-wave drive, this
protocol is not subject to stability requirements that normally limit the
strength of achievable entanglement. We investigate the protocol's performance
under realistic conditions, including mechanical decoherence, in full detail.
We discuss the relevance of a high mechanical Qf product for entanglement
creation and provide a quantitative statement on which magnitude of the Qf
product is necessary for a successful realization of the scheme. We determine
the optimal parameter regime for its operation and show it to work in current
state-of-the-art systems.Comment: 10 pages, 2 figure
Novel aspects of age-protection by spermidine supplementation are associated with preserved telomere length
Ageing provokes a plethora of molecular, cellular and physiological deteriorations, including heart failure, neurodegeneration, metabolic maladaptation, telomere attrition and hair loss. Interestingly, on the molecular level, the capacity to induce autophagy, a cellular recycling and cleaning process, declines with age across a large spectrum of model organisms and is thought to be responsible for a subset of age-induced changes. Here, we show that a 6-month administration of the natural autophagy inducer spermidine in the drinking water to aged mice is sufficient to significantly attenuate distinct age-associated phenotypes. These include modulation of brain glucose metabolism, suppression of distinct cardiac inflammation parameters, decreased number of pathological sights in kidney and liver and decrease of age-induced hair loss. Interestingly, spermidine-mediated age protection was associated with decreased telomere attrition, arguing in favour of a novel cellular mechanism behind the anti-ageing effects of spermidine administration
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An overview of the first decade of PollyNET: An emerging network of automated Raman-polarization lidars for continuous aerosol profiling
A global vertically resolved aerosol data set covering more than 10 years of observations at more than 20 measurement sites distributed from 63° N to 52° S and 72° W to 124° E has been achieved within the Raman and polarization lidar network PollyNET. This network consists of portable, remote-controlled multiwavelength-polarization-Raman lidars (Polly) for automated and continuous 24/7 observations of clouds and aerosols. PollyNET is an independent, voluntary, and scientific network. All Polly lidars feature a standardized instrument design with different capabilities ranging from single wavelength to multiwavelength systems, and now apply unified calibration, quality control, and data analysis. The observations are processed in near-real time without manual intervention, and are presented online at http://polly.tropos.de/. The paper gives an overview of the observations on four continents and two research vessels obtained with eight Polly systems. The specific aerosol types at these locations (mineral dust, smoke, dust-smoke and other dusty mixtures, urban haze, and volcanic ash) are identified by their Ångström exponent, lidar ratio, and depolarization ratio. The vertical aerosol distribution at the PollyNET locations is discussed on the basis of more than 55 000 automatically retrieved 30 min particle backscatter coefficient profiles at 532 nm as this operating wavelength is available for all Polly lidar systems. A seasonal analysis of measurements at selected sites revealed typical and extraordinary aerosol conditions as well as seasonal differences. These studies show the potential of PollyNET to support the establishment of a global aerosol climatology that covers the entire troposphere
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