2,367 research outputs found
Cryogenic Q-factor measurement of optical substrates for optimization of gravitational wave detectors
Future generations of gravitational wave interferometers are likely to be operated at cryogenic temperatures because one of the sensitivity limiting factors of the present generation is the thermal noise of end mirrors and beam splitters that occurs in the optical substrates as well as in the dielectric coatings. A possible method for minimizing thermal noise is cooling to cryogenic temperatures, maximizing the mechanical quality factor Q, and maximizing the eigenfrequencies of the substrate. We present experimental details of a new cryogenic apparatus that is suitable for the measurement of the temperature-dependent Q-factor of reflective, transmissive as well as nano-structured grating optics down to 5 K. In particular, the SQUID-based and the optical interferometric approaches to the measurement of the amplitude of vibrating test bodies are compared and the method of ring-down recording is described
PHYLOGENY OF THE ARCHAEBACTERIA AND EUKARYOTES: HOMOLOGY OF THE DNA-DEPENDENT RNA POLYMERASES
The Cambrian-Precambrian contact in northwestern Connecticut and west-central Massachusetts
Guidebook for field trips in western Massachusetts, northern Connecticut and adjacent areas of New York: 67th annual meeting October 10, 11, and 12, 1975: Trip B-5; C-
Recovery of continuous wave squeezing at low frequencies
We propose and demonstrate a system that produces squeezed vacuum using a
pair of optical parametric amplifiers. This scheme allows the production of
phase sidebands on the squeezed vacuum which facilitate phase locking in
downstream applications. We observe strong, stably locked, continuous wave
vacuum squeezing at frequencies as low as 220 kHz. We propose an alternative
resonator configuration to overcome low frequency squeezing degradation caused
by the optical parametric amplifiers.Comment: 9 pages, 4 figure
Changes in union membership over time : a panel analysis for West Germany
Despite the apparent stability of the wage bargaining institutions in West Germany, aggregate union membership has been declining dramatically since the early 90's. However, aggregate gross membership numbers do not distinguish by employment status and it is impossible to disaggregate these sufficiently. This paper uses four waves of the German Socioeconomic Panel in 1985, 1989, 1993, and 1998 to perform a panel analysis of net union membership among employees. We estimate a correlated random effects probit model suggested in Chamberlain (1984) to take proper account of individual specfic effects. Our results suggest that at the individual level the propensity to be a union member has not changed considerably over time. Thus, the aggregate decline in membership is due to composition effects. We also use the estimates to predict net union density at the industry level based on the IAB employment subsample for the time period 1985 to 1997. JEL - Klassifikation: J
The GEO600 squeezed light source
The next upgrade of the GEO600 gravitational wave detector is scheduled for
2010 and will, in particular, involve the implementation of squeezed light. The
required non-classical light source is assembled on a 1.5m^2 breadboard and
includes a full coherent control system and a diagnostic balanced homodyne
detector. Here, we present the first experimental characterization of this
setup as well as a detailed description of its optical layout. A squeezed
quantum noise of up to 9dB below the shot-noise level was observed in the
detection band between 10Hz and 10kHz. We also present an analysis of the
optical loss in our experiment and provide an estimation of the possible
non-classical sensitivity improvement of the future squeezed light enhanced
GEO600 detector.Comment: 8 pages, 4 figure
Towards Einstein-Podolsky-Rosen quantum channel multiplexing
A single broadband squeezed field constitutes a quantum communication
resource that is sufficient for the realization of a large number N of quantum
channels based on distributed Einstein-Podolsky-Rosen (EPR) entangled states.
Each channel can serve as a resource for, e.g. independent quantum key
distribution or teleportation protocols. N-fold channel multiplexing can be
realized by accessing 2N squeezed modes at different Fourier frequencies. We
report on the experimental implementation of the N=1 case through the
interference of two squeezed states, extracted from a single broadband squeezed
field, and demonstrate all techniques required for multiplexing (N>1). Quantum
channel frequency multiplexing can be used to optimize the exploitation of a
broadband squeezed field in a quantum information task. For instance, it is
useful if the bandwidth of the squeezed field is larger than the bandwidth of
the homodyne detectors. This is currently a typical situation in many
experiments with squeezed and two-mode squeezed entangled light.Comment: 4 pages, 4 figures. In the new version we cite recent experimental
work bei Mehmet et al., arxiv0909.5386, in order to clarify the motivation of
our work and its possible applicatio
Direct Sampling of Negative Quasiprobabilities of a Squeezed State
Although squeezed states are nonclassical states, so far, their
nonclassicality could not be demonstrated by negative quasiprobabilities. In
this work we derive pattern functions for the direct experimental determination
of so-called nonclassicality quasiprobabilities. The negativities of these
quantities turn out to be necessary and sufficient for the nonclassicality of
an arbitrary quantum state and are therefore suitable for a direct and general
test of nonclassicality. We apply the method to a squeezed vacuum state of
light that was generated by parametric down-conversion in a second-order
nonlinear crystal.Comment: 4 pages, 4 figures, supplementary material adde
Entangled Qubits in a non-Gaussian Quantum State
We experimentally generate and tomographically characterize a mixed, genuinely non-Gaussian bipartite continuous-variable entangled state. By testing entanglement in 22-dimensional two-qubit subspaces, entangled qubits are localized within the density matrix, which, firstly, proves the distillability of the state and, secondly, is useful to estimate the efficiency and test the applicability of distillation protocols. In our example, the entangled qubits are arranged in the density matrix in an asymmetric way, i.e. entanglement is found between diverse qubits composed of different photon number states, although the entangled state is symmetric under exchanging the modes
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