37 research outputs found
Observation of squeezed light with 10dB quantum noise reduction
Squeezing of light's quantum noise requires temporal rearranging of photons.
This again corresponds to creation of quantum correlations between individual
photons. Squeezed light is a non-classical manifestation of light with great
potential in high-precision quantum measurements, for example in the detection
of gravitational waves. Equally promising applications have been proposed in
quantum communication. However, after 20 years of intensive research doubts
arose whether strong squeezing can ever be realized as required for eminent
applications. Here we show experimentally that strong squeezing of light's
quantum noise is possible. We reached a benchmark squeezing factor of 10 in
power (10dB). Thorough analysis reveals that even higher squeezing factors will
be feasible in our setup.Comment: 10 pages, 4 figure
Coating-free mirrors for high precision interferometric experiments
Thermal noise in mirror optical coatings may not only limit the sensitivity of future gravitational-wave
detectors in their most sensitive frequency band but is also a major impediment for experiments that aim to
reach the standard quantum limit or cool mechanical systems to their quantum ground state. We present the
design and experimental characterization of a highly reflecting mirror without any optical coating. This
coating-free mirror is based on total internal reflection and Brewster-angle coupling. In order to characterize its
performance, the coating-free mirror was incorporated into a triangular ring cavity together with a high quality
conventional mirror. The finesse of this cavity was measured using an amplitude transfer function to be about
F 4000. This finesse corresponds to a reflectivity of the coating-free mirror of about R 99.89%. In addition,
the dependence of the reflectivity on rotation was mapped out
Interferometer readout-noise below the Standard Quantum Limit of a membrane
Here we report on the realization of a Michelson-Sagnac interferometer whose
purpose is the precise characterization of the motion of membranes showing
significant light transmission. Our interferometer has a readout noise spectral
density (imprecision) of 3E-16 m/sqrt(Hz) at frequencies around the fundamental
resonance of a SiN_x membrane at about 100 kHz, without using optical cavities.
The readout noise demonstrated is more than 16 dB below the peak value of the
membrane's standard quantum limit (SQL). This reduction is significantly higher
than those of previous works with nano-wires [Teufel et al., Nature Nano. 4,
820 (2009); Anetsberger et al., Nature Phys. 5, 909 (2009)]. We discuss the
meaning of the SQL for force measurements and its relation to the readout
performance and conclude that neither our nor previous experiments achieved a
total noise spectral density as low as the SQL
Frequency dependence of thermal noise in gram-scale cantilever flexures
We present measurements of the frequency dependence of thermal noise in aluminum and niobium flexures. Our measurements cover the audio-frequency band from 10 Hz to 10 kHz, which is of particular relevance to ground-based interferometric gravitational wave detectors, and span up to an order of magnitude above and below the fundamental flexure resonances. Results from two flexures are well explained by a simple model in which both structural and thermoelastic loss play a role. The ability of such a model to explain this interplay is important for investigations of quantum-radiation-pressure noise and the standard quantum limit. Furthermore, measurements on a third flexure provide evidence that surface damage can affect the frequency dependence of thermal noise in addition to reducing the quality factor, a result which will aid the understanding of how aging effects impact on thermal noise behavior.Australian Research Counci
Searching for stochastic gravitational-wave background with the co-located LIGO interferometers
This paper presents techniques developed by the LIGO Scientific Collaboration
to search for the stochastic gravitational-wave background using the co-located
pair of LIGO interferometers at Hanford, WA. We use correlations between
interferometers and environment monitoring instruments, as well as time-shifts
between two interferometers (described here for the first time) to identify
correlated noise from non-gravitational sources. We veto particularly noisy
frequency bands and assess the level of residual non-gravitational coupling
that exists in the surviving data.Comment: Proceedings paper from the 7th Edoardo Amaldi Conference on
Gravitational Waves, held in Sydney, Australia from 8-14 July 2007. Accepted
to J. Phys.: Conf. Se
The 10m AEI prototype facility A brief overview
The AEI 10 m prototype interferometer facility is currently being constructed
at the Albert Einstein Institute in Hannover, Germany. It aims to perform
experiments for future gravitational wave detectors using advanced techniques.
Seismically isolated benches are planned to be interferometrically
interconnected and stabilized, forming a low-noise testbed inside a 100 m^3
ultra-high vacuum system. A well-stabilized high power laser will perform
differential position readout of 100 g test masses in a 10 m suspended
arm-cavity enhanced Michelson interferometer at the crossover of measurement
(shot) noise and backaction (quantum radiation pressure) noise, the so-called
Standard Quantum Limit (SQL). Such a sensitivity enables experiments in the
highly topical field of macroscopic quantum mechanics. In this article we
introduce the experimental facility and describe the methods employed,
technical details of subsystems will be covered in future papers
Detection Confidence Tests for Burst and Inspiral Candidate Events
The LIGO Scientific Collaboration (LSC) is developing and running analysis
pipelines to search for gravitational-wave transients emitted by astrophysical
events such as compact binary mergers or core-collapse supernovae. However,
because of the non-Gaussian, non-stationary nature of the noise exhibited by
the LIGO detectors, residual false alarms might be found at the end of the
pipelines. A critical aspect of the search is then to assess our confidence for
gravitational waves and to distinguish them from those false alarms. Both the
'Compact Binary Coalescence' and the 'Burst' working groups have been
developing a detection checklist for the validation of candidate-events,
consisting of a series of tests which aim to corroborate a detection or to
eliminate a false alarm. These tests include for example data quality checks,
analysis of the candidate appearance, parameter consistency studies and
coherent analysis. In this paper, the general methodology used for candidate
validation is presented. The method is illustrated with an example of simulated
gravitational-wave signal and a false alarm.Comment: 15 pages, 8 figures, Contribution to 12th Gravitational Wave Data
Analysis Workshop. Version sent to Classical and Quantum Gravity immediately
before publication. It addresses the CQG referee's comment
Quantum state preparation and macroscopic entanglement in gravitational-wave detectors
Long-baseline laser-interferometer gravitational-wave detectors are operating
at a factor of 10 (in amplitude) above the standard quantum limit (SQL) within
a broad frequency band. Such a low classical noise budget has already allowed
the creation of a controlled 2.7 kg macroscopic oscillator with an effective
eigenfrequency of 150 Hz and an occupation number of 200. This result, along
with the prospect for further improvements, heralds the new possibility of
experimentally probing macroscopic quantum mechanics (MQM) - quantum mechanical
behavior of objects in the realm of everyday experience - using
gravitational-wave detectors. In this paper, we provide the mathematical
foundation for the first step of a MQM experiment: the preparation of a
macroscopic test mass into a nearly minimum-Heisenberg-limited Gaussian quantum
state, which is possible if the interferometer's classical noise beats the SQL
in a broad frequency band. Our formalism, based on Wiener filtering, allows a
straightforward conversion from the classical noise budget of a laser
interferometer, in terms of noise spectra, into the strategy for quantum state
preparation, and the quality of the prepared state. Using this formalism, we
consider how Gaussian entanglement can be built among two macroscopic test
masses, and the performance of the planned Advanced LIGO interferometers in
quantum-state preparation
Searching for a Stochastic Background of Gravitational Waves with LIGO
The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed
the fourth science run, S4, with significantly improved interferometer
sensitivities with respect to previous runs. Using data acquired during this
science run, we place a limit on the amplitude of a stochastic background of
gravitational waves. For a frequency independent spectrum, the new limit is
. This is currently the most sensitive
result in the frequency range 51-150 Hz, with a factor of 13 improvement over
the previous LIGO result. We discuss complementarity of the new result with
other constraints on a stochastic background of gravitational waves, and we
investigate implications of the new result for different models of this
background.Comment: 37 pages, 16 figure