617 research outputs found
Quantum feedback cooling of a single trapped ion in front of a mirror
We develop a theory of quantum feedback cooling of a single ion trapped in
front of a mirror. By monitoring the motional sidebands of the light emitted
into the mirror mode we infer the position of the ion, and act back with an
appropriate force to cool the ion. We derive a feedback master equation along
the lines of the quantum feedback theory developed by Wiseman and Milburn,
which provides us with cooling times and final temperatures as a function of
feedback gain and various system parameters.Comment: 15 pages, 11 Figure
The photon blockade effect in optomechanical systems
We analyze the photon statistics of a weakly driven optomechanical system and
discuss the effect of photon blockade under single photon strong coupling
conditions. We present an intuitive interpretation of this effect in terms of
displaced oscillator states and derive analytic expressions for the cavity
excitation spectrum and the two photon correlation function . Our
results predict the appearance of non-classical photon correlations in the
combined strong coupling and sideband resolved regime, and provide a first
detailed understanding of photon-photon interactions in strong coupling
optomechanics
Influence of monolayer contamination on electric-field-noise heating in ion traps
Electric field noise is a hinderance to the assembly of large scale quantum
computers based on entangled trapped ions. Apart from ubiquitous technical
noise sources, experimental studies of trapped ion heating have revealed
additional limiting contributions to this noise, originating from atomic
processes on the electrode surfaces. In a recent work [A. Safavi-Naini et al.,
Phys. Rev. A 84, 023412 (2011)] we described a microscopic model for this
excess electric field noise, which points a way towards a more systematic
understanding of surface adsorbates as progenitors of electric field jitter
noise. Here, we address the impact of surface monolayer contamination on
adsorbate induced noise processes. By using exact numerical calculations for H
and N atomic monolayers on an Au(111) surface representing opposite extremes of
physisorption and chemisorption, we show that an additional monolayer can
significantly affect the noise power spectrum and either enhance or suppress
the resulting heating rates.Comment: 8 pages, 5 figure
Reservoir engineering and dynamical phase transitions in optomechanical arrays
We study the driven-dissipative dynamics of photons interacting with an array
of micromechanical membranes in an optical cavity. Periodic membrane driving
and phonon creation result in an effective photon-number conserving non-unitary
dynamics, which features a steady state with long-range photonic coherence. If
the leakage of photons out of the cavity is counteracted by incoherent driving
of the photonic modes, we show that the system undergoes a dynamical phase
transition to the state with long-range coherence. A minimal system, composed
of two micromechanical membranes in a cavity, is studied in detail, and it is
shown to be a realistic setup where the key processes of the driven-dissipative
dynamics can be seen.Comment: 16 pages, 9 figure
Autonomous distribution of programmable multi-qubit entanglement in a dual-rail quantum network
We propose and analyze a scalable and fully autonomous scheme for preparing
spatially distributed multi-qubit entangled states in a dual-rail waveguide QED
setup. In this approach, arrays of qubits located along two separated
waveguides are illuminated by correlated photons from the output of a
non-degenerate parametric amplifier. These photons drive the qubits into
different classes of pure entangled steady states, for which the degree of
multipartite entanglement can be conveniently adjusted by the chosen pattern of
local qubit-photon detunings. Numerical simulations for moderate-sized networks
show that the preparation time for these complex multi-qubit states increases
at most linearly with the system size and that one may benefit from an
additional speedup in the limit of a large amplifier bandwidth. Therefore, this
scheme offers an intriguing new route for distributing ready-to-use
multipartite entangled states across large quantum networks, without requiring
any precise pulse control and relying on a single Gaussian entanglement source
only.Comment: Main: 7 pages and 4 figures; Supplementary material: 6 pages and 2
figure
Quantitative evaluation of orofacial motor function in mice: The pasta gnawing test, a voluntary and stress-free behavior test
AbstractBackgroundEvaluation of motor deficits in rodents is mostly restricted to limb motor tests that are often high stressors for the animals.New methodTo test rodents for orofacial motor impairments in a stress-free environment, we established the pasta gnawing test by measuring the biting noise of mice that eat a piece of spaghetti. Two parameters were evaluated, the biting speed and the biting peaks per biting episode. To evaluate the power of this test compared to commonly used limb motor and muscle strength tests, three mouse models of Parkinson’s disease, amyotrophic lateral sclerosis and Niemann-Pick disease were tested in the pasta gnawing test, RotaRod and wire suspension test.ResultsOur results show that the pasta gnawing test reliably displays orofacial motor deficits.Comparison with existing methodsThe test is especially useful as additional motor test in early onset disease models, since it shows first deficits later than the RotaRod or wire suspension test. The test depends on a voluntary eating behavior of the animal with only a short-time food deprivation and should thus be stress-free.ConclusionsThe pasta gnawing test represents a valuable tool to analyze orofacial motor deficits in different early onset disease models
Generation of Squeezed States of Nanomechanical Resonators by Reservoir Engineering
An experimental demonstration of a non-classical state of a nanomechanical
resonator is still an outstanding task. In this paper we show how the resonator
can be cooled and driven into a squeezed state by a bichromatic microwave
coupling to a charge qubit. The stationary oscillator state exhibits a reduced
noise in one of the quadrature components by a factor of 0.5 - 0.2. These
values are obtained for a 100 MHz resonator with a Q-value of 10 to 10
and for support temperatures of T 25 mK. We show that the coupling to
the charge qubit can also be used to detect the squeezed state via measurements
of the excited state population. Furthermore, by extending this measurement
procedure a complete quantum state tomography of the resonator state can be
performed. This provides a universal tool to detect a large variety of
different states and to prove the quantum nature of a nanomechanical
oscillator.Comment: 13 pages,9 figure
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How to Measure the Optical Quality of Focussing Solar Collectors without Laser Ray Tracing
Designers and Manufacturers need a tool for evaluating the optical quality of solar concentrators. This paper describes a novel alternative to the laser ray trace technique
Feedback cooling of a single trapped ion
Based on a real-time measurement of the motion of a single ion in a Paul
trap, we demonstrate its electro-mechanical cooling below the Doppler limit by
homodyne feedback control (cold damping). The feedback cooling results are well
described by a model based on a quantum mechanical Master Equation.Comment: 4 pages, 3 figure
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