118 research outputs found
Sensitivity below the standard quantum limit in gravitational wave detectors with Michelson-Fabry-Perot readout
We calculate the quantum noise limited displacement sensitivity of a
Michelson-Fabry-Perot (MFP) with detuned cavities, followed by phase-sensitive
homodyne detection. We show that the standard quantum limit can be surpassed
even with resonant cavities and without any signal-recycling mirror nor
additional cavities. Indeed, thanks to the homodyne detection, the output field
quadrature can be chosen in such a way to cancel the effect of input amplitude
fluctuations, i.e., eliminating the force noise. With detuned cavities, the
modified opto-mechanical susceptivity allows to reach unlimited sensitivity for
large enough (yet finite) optical power. Our expressions include mirror losses
and cavity delay effect, for a realistic comparison with experiments. Our study
is particularly devoted to gravitational wave detectors and we consider both an
interferometer with free-falling mirrors, and a MFP as readout for a massive
detector. In the latter case, the sensitivity curve of the recently conceived
'DUAL' detector, based on two acoustic modes, is obtained
Dual channel self-oscillating optical magnetometer
We report on a two-channel magnetometer based on nonlinear magneto-optical
rotation in a Cs glass cell with buffer gas. The Cs atoms are optically pumped
and probed by free running diode lasers tuned to the D line. A wide
frequency modulation of the pump laser is used to produce both synchronous
Zeeman optical pumping and hyperfine repumping. The magnetometer works in an
unshielded environment and spurious signal from distant magnetic sources is
rejected by means of differential measurement. In this regime the magnetometer
simultaneously gives the magnetic field modulus and the field difference.
Rejection of the common-mode noise allows for high-resolution magnetometry
with a sensitivity of \pthz{2}. This sensitivity, in conjunction with long-term
stability and a large bandwidth, makes possible to detect water proton
magnetization and its free induction decay in a measurement volume of 5 cmComment: 13 pages, 9 figures. Improved version (v2). Accepted for publicatio
Unraveling the Skillsets of Data Scientists: Text Mining Analysis of Dutch University Master Programs in Data Science and Artificial Intelligence
The growing demand for data scientists in the global labor market and the
Netherlands has led to a rise in data science and artificial intelligence (AI)
master programs offered by universities. However, there is still a lack of
clarity regarding the specific skillsets of data scientists. This study aims to
address this issue by employing Correlated Topic Modeling (CTM) to analyse the
content of 41 master programs offered by seven Dutch universities. We assess
the differences and similarities in the core skills taught by these programs,
determine the subject-specific and general nature of the skills, and provide a
comparison between the different types of universities offering these programs.
Our findings reveal that research, data processing, statistics and ethics are
the predominant skills taught in Dutch data science and AI master programs,
with general universities emphasizing research skills and technical
universities focusing more on IT and electronic skills. This study contributes
to a better understanding of the diverse skillsets of data scientists, which is
essential for employers, universities, and prospective students
Rotational sensitivity of the "G-Pisa" gyrolaser
G-Pisa is an experiment investigating the possibility to operate a high
sensitivity laser gyroscope with area less than for improving the
performances of the mirrors suspensions of the gravitational wave antenna
Virgo. The experimental set-up consists in a He-Ne ring laser with a 4 mirrors
square cavity. The laser is pumped by an RF discharge where the RF oscillator
includes the laser plasma in order to reach a better stability. The contrast of
the Sagnac fringes is typically above 50% and a stable regime has been reached
with the laser operating both single mode or multimode. The effect of hydrogen
contamination on the laser was also checked. A low-frequency sensitivity, below
, in the range of has been
measured.Comment: 6 pages, 6 figures, presented at the EFTF-IFCS joint conference 200
Interferometric length metrology for the dimensional control of ultra-stable Ring Laser Gyroscopes
We present the experimental test of a method for controlling the absolute
length of the diagonals of square ring laser gyroscopes. The purpose is to
actively stabilize the ring cavity geometry and to enhance the rotation sensor
stability in order to reach the requirements for the detection of the
relativistic Lense-Thirring effect with a ground-based array of optical
gyroscopes. The test apparatus consists of two optical cavities 1.32 m in
length, reproducing the features of the ring cavity diagonal resonators of
large frame He-Ne ring laser gyroscopes. The proposed measurement technique is
based on the use of a single diode laser, injection locked to a frequency
stabilized He-Ne/Iodine frequency standard, and a single electro-optic
modulator. The laser is modulated with a combination of three frequencies
allowing to lock the two cavities to the same resonance frequency and, at the
same time, to determine the cavity Free Spectral Range (FSR). We obtain a
stable lock of the two cavities to the same optical frequency reference,
providing a length stabilization at the level of 1 part in , and the
determination of the two FSRs with a relative precision of 0.2 ppm. This is
equivalent to an error of 500 nm on the absolute length difference between the
two cavities
Horizontal rotation signals detected by "G-Pisa" ring laser for the Mw=9.0, March 2011, Japan earthquake
We report the observation of the ground rotation induced by the Mw=9.0, 11th
of March 2011, Japan earthquake. The rotation measurements have been conducted
with a ring laser gyroscope operating in a vertical plane, thus detecting
rotations around the horizontal axis. Comparison of ground rotations with
vertical accelerations from a co-located force-balance accelerometer shows
excellent ring laser coupling at periods longer than 100s. Under the plane wave
assumption, we derive a theoretical relationship between horizontal rotation
and vertical acceleration for Rayleigh waves. Due to the oblique mounting of
the gyroscope with respect to the wave direction-of-arrival, apparent
velocities derived from the acceleration / rotation rate ratio are expected to
be always larger than, or equal to the true wave propagation velocity. This
hypothesis is confirmed through comparison with fundamental-mode, Rayleigh wave
phase velocities predicted for a standard Earth model.Comment: Accepted for publication in Journal of Seismolog
A 1.82 m^2 ring laser gyroscope for nano-rotational motion sensing
We present a fully active-controlled He-Ne ring laser gyroscope, operating in
square cavity 1.35 m in side. The apparatus is designed to provide a very low
mechanical and thermal drift of the ring cavity geometry and is conceived to be
operative in two different orientations of the laser plane, in order to detect
rotations around the vertical or the horizontal direction. Since June 2010 the
system is active inside the Virgo interferometer central area with the aim of
performing high sensitivity measurements of environmental rotational noise. So
far, continuous not attempted operation of the gyroscope has been longer than
30 days. The main characteristics of the laser, the active remote-controlled
stabilization systems and the data acquisition techniques are presented. An
off-line data processing, supported by a simple model of the sensor, is shown
to improve the effective long term stability. A rotational sensitivity at the
level of ten nanoradiants per squareroot of Hz below 1 Hz, very close to the
required specification for the improvement of the Virgo suspension control
system, is demonstrated for the configuration where the laser plane is
horizontal
Geometrical scale-factor stabilization of square cavity ring laser gyroscopes
Large frame ring laser gyros performances are ultimately limited by the instabilities of their geometrical parameters. We present the experimental activity on the GP2 ring laser gyro. GP2 is a ring laser gyro devoted to develop advanced stabilization techniques of the ring cavity geometrical scale-factor. A method based on optical interferometry has been developed for canceling the deformations of the resonator. The method is based on the measurement and stabilization of the absolute length of the cavity perimeter and of the resonators formed by the opposite cavity mirrors. The optical frequency reference in the experiment is an iodine-stabilized He-Ne laser, with a relative frequency stability of 10-11. The measurement of the absolute length of the two resonators has been demonstrated up to now on a test bench. We discuss the experimental results on GP2: the present performances as a ring laser gyro and the stabilization scheme to be implemented in the near future
- …