28,566 research outputs found
Squeezed light at 1550 nm with a quantum noise reduction of 12.3 dB
Continuous-wave squeezed states of light at the wavelength of 1550 nm have
recently been demonstrated, but so far the obtained factors of noise
suppression still lag behind today's best squeezing values demonstrated at 1064
nm. Here we report on the realization of a half-monolithic nonlinear resonator
based on periodically-poled potassium titanyl phosphate which enabled the
direct detection of up to 12.3 dB of squeezing at 5 MHz. Squeezing was observed
down to a frequency of 2 kHz which is well within the detection band of
gravitational wave interferometers. Our results suggest that a long-term stable
1550 nm squeezed light source can be realized with strong squeezing covering
the entire detection band of a 3rd generation gravitational-wave detector such
as the Einstein Telescope
Decorrelation of neural-network activity by inhibitory feedback
Correlations in spike-train ensembles can seriously impair the encoding of
information by their spatio-temporal structure. An inevitable source of
correlation in finite neural networks is common presynaptic input to pairs of
neurons. Recent theoretical and experimental studies demonstrate that spike
correlations in recurrent neural networks are considerably smaller than
expected based on the amount of shared presynaptic input. By means of a linear
network model and simulations of networks of leaky integrate-and-fire neurons,
we show that shared-input correlations are efficiently suppressed by inhibitory
feedback. To elucidate the effect of feedback, we compare the responses of the
intact recurrent network and systems where the statistics of the feedback
channel is perturbed. The suppression of spike-train correlations and
population-rate fluctuations by inhibitory feedback can be observed both in
purely inhibitory and in excitatory-inhibitory networks. The effect is fully
understood by a linear theory and becomes already apparent at the macroscopic
level of the population averaged activity. At the microscopic level,
shared-input correlations are suppressed by spike-train correlations: In purely
inhibitory networks, they are canceled by negative spike-train correlations. In
excitatory-inhibitory networks, spike-train correlations are typically
positive. Here, the suppression of input correlations is not a result of the
mere existence of correlations between excitatory (E) and inhibitory (I)
neurons, but a consequence of a particular structure of correlations among the
three possible pairings (EE, EI, II)
Experiments with calibrated digital sideband separating downconversion
This article reports on the first step in a focused program to re-optimize
radio astronomy receiver architecture to better take advantage of the latest
advancements in commercial digital technology. Specifically, an L-Band
sideband-separating downconverter has been built using a combination of careful
(but ultimately very simple) analog design and digital signal processing to
achieve wideband downconversion of an RFI-rich frequency spectrum to baseband
in a single mixing step, with a fixed-frequency Local Oscillator and stable
sideband isolation exceeding 50 dB over a 12 degree C temperature range.Comment: 10 pages, 12 figures, to be published in PAS
The STAR MAPS-based PiXeL detector
The PiXeL detector (PXL) for the Heavy Flavor Tracker (HFT) of the STAR
experiment at RHIC is the first application of the state-of-the-art thin
Monolithic Active Pixel Sensors (MAPS) technology in a collider environment.
Custom built pixel sensors, their readout electronics and the detector
mechanical structure are described in detail. Selected detector design aspects
and production steps are presented. The detector operations during the three
years of data taking (2014-2016) and the overall performance exceeding the
design specifications are discussed in the conclusive sections of this paper
Optomechanical detection of weak forces
Optomechanical systems are often used for the measurement of weak forces.
Feedback loops can be used in these systems for achieving noise reduction. Here
we show that even though feedback is not able to improve the signal to noise
ratio of the device in stationary conditions, it is possible to design a
nonstationary strategy able to improve the sensitivity.Comment: 12 pages, 6 figures, contribution to the proceedings of the SPIE
Conference on Fluctuations and Nois
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