14 research outputs found
Bilinear noise subtraction at the GEO 600 observatory
We develop a scheme to subtract off bilinear noise from the gravitational wave strain data and demonstrate it at the GEO 600 observatory. Modulations caused by test mass misalignments on longitudinal control signals are observed to have a broadband effect on the mid-frequency detector sensitivity ranging from 50 Hz to 500 Hz. We estimate this bilinear coupling by making use of narrow-band signal injections that are already in place for noise projection purposes. A coherent bilinear signal is constructed by a two-stage system identification process where the involved couplings are approximated in terms of stable rational functions. The time-domain filtering efficiency is observed to depend upon the system identification process especially when the involved transfer functions cover a large dynamic range and have multiple resonant features. We improve upon the existing filter design techniques by employing a Bayesian adaptive directed search strategy that optimizes across the several key parameters that affect the accuracy of the estimated model. The resulting post-offline subtraction leads to a suppression of modulation side-bands around the calibration lines along with a broadband reduction of the mid-frequency noise floor. The filter coefficients are updated periodically to account for any non-stationarities that can arise within the coupling. The observed increase in the astrophysical range and a reduction in the occurrence of non-astrophysical transients suggest that the above method is a viable data cleaning technique for current and future gravitational wave observatories
High power and ultra-low-noise photodetector for squeezed-light enhanced gravitational wave detectors
Current laser-interferometric gravitational wave detectors employ a self-homodyne
readout scheme where a comparatively large light power (5â50 mW) is detected per photosensitive
element. For best sensitivity to gravitational waves, signal levels as low as the quantum
shot noise have to be measured as accurately as possible. The electronic noise of the detection
circuit can produce a relevant limit to this accuracy, in particular when squeezed states of light
are used to reduce the quantum noise. We present a new electronic circuit design reducing the
electronic noise of the photodetection circuit in the audio band. In the application of this circuit at
the gravitational-wave detector GEO 600 the shot-noise to electronic noise ratio was permanently
improved by a factor of more than 4 above 1 kHz, while the dynamic range was improved by
a factor of 7. The noise equivalent photocurrent of the implemented photodetector and circuit
is about 5 ”A/
â\ud
Hz above 1 kHz with a maximum detectable photocurrent of 20 mA. With the
new circuit, the observed squeezing level in GEO 600 increased by 0.2 dB. The new circuit also
creates headroom for higher laser power and more squeezing to be observed in the future in
GEO 600 and is applicable to other optics experiments
First demonstration of 6 dB quantum noise reduction in a kilometer scale gravitational wave observatory
Photon shot noise, arising from the quantum-mechanical nature of the light,
currently limits the sensitivity of all the gravitational wave observatories at
frequencies above one kilohertz. We report a successful application of squeezed
vacuum states of light at the GEO\,600 observatory and demonstrate for the
first time a reduction of quantum noise up to dB in a
kilometer-scale interferometer. This is equivalent at high frequencies to
increasing the laser power circulating in the interferometer by a factor of
four. Achieving this milestone, a key goal for the upgrades of the advanced
detectors, required a better understanding of the noise sources and losses, and
implementation of robust control schemes to mitigate their contributions. In
particular, we address the optical losses from beam propagation, phase noise
from the squeezing ellipse, and backscattered light from the squeezed light
source. The expertise gained from this work carried out at GEO 600 provides
insight towards the implementation of 10 dB of squeezing envisioned for
third-generation gravitational wave detectors
Characterization and evasion of backscattered light in the squeezed-light enhanced gravitational wave interferometer GEO 600
Squeezed light is injected into the dark port of gravitational wave
interferometers, in order to reduce the quantum noise. A fraction of the
interferometer output light can reach the OPO due to sub-optimal isolation of
the squeezing injection path. This backscattered light interacts with squeezed
light generation process, introducing additional measurement noise. We present
a theoretical description of the noise coupling mechanism. We propose a control
scheme to achieve a de-amplification of the backscattered light inside the OPO
with a consequent reduction of the noise caused by it. The scheme was
implemented at the GEO 600 detector and has proven to be crucial in maintaining
a good level of quantum noise reduction of the interferometer for high
parametric gain of the OPO. In particular, the mitigation of the backscattered
light noise helped in reaching 6dB of quantum noise reduction [Phys. Rev. Lett.
126, 041102 (2021)]. The impact of backscattered-light-induced noise on the
squeezing performance is phenomenologically equivalent to increased phase noise
of the squeezing angle control. The results discussed in this paper provide a
way for a more accurate estimation of the residual phase noise of the squeezed
light field.Comment: 14 pages, 6 figure
Characterization and evasion of backscattered light in the squeezed-light enhanced gravitational wave interferometer GEO 600
Squeezed light is injected into the dark port of gravitational wave interferometers, in order to reduce the quantum noise. A fraction of the interferometer output light can reach the OPO due to sub-optimal isolation of the squeezing injection path. This backscattered light interacts with squeezed light generation process, introducing additional measurement noise. We present a theoretical description of the noise coupling mechanism and we prove the model with experimental results. We propose a control scheme to achieve a de-amplification of the backscattered light inside the OPO with a consequent reduction of the noise caused by it. The scheme was implemented at the GEO 600 detector and has proven to be crucial in maintaining a good level of quantum noise reduction of the interferometer for high parametric gain of the OPO. In particular, the mitigation of the backscattered light noise helped in reaching 6 dB of quantum noise reduction [Phys. Rev. Lett. 126, 041102 (2021)]. We show that the impact of backscattered-light-induced noise on the squeezing performance is phenomenologically equivalent to increased phase noise of the squeezing angle control. The results discussed in this paper provide a way for a more accurate estimation of the residual phase noise of the squeezed light field. Finally, the knowledge of the backscattered light noise coupling mechanism is a useful tool to inform the design of the squeezing injection path in terms of path stability and optical isolation
Direct limits for scalar field dark matter from a gravitational-wave detector
The nature of dark matter remains unknown to date, although several candidate particles are being considered in a dynamically changing research landscape1. Scalar field dark matter is a prominent option that is being explored with precision instruments, such as atomic clocks and optical cavities2â8. Here we describe a direct search for scalar field dark matter using a gravitational-wave detector, which operates beyond the quantum shot-noise limit. We set new upper limits on the coupling constants of scalar field dark matter as a function of its mass, by excluding the presence of signals that would be produced through the direct coupling of this dark matter to the beam splitter of the GEO600 interferometer. These constraints improve on bounds from previous direct searches by more than six orders of magnitude and are, in some cases, more stringent than limits obtained in tests of the equivalence principle by up to four orders of magnitude. Our work demonstrates that scalar field dark matter can be investigated or constrained with direct searches using gravitational-wave detectors and highlights the potential of quantum-enhanced interferometry for dark matter detection. © 2021, The Author(s)
Direct limits for scalar field dark matter from a gravitational-wave detector
The nature of dark matter remains unknown to date; several candidate
particles are being considered in a dynamically changing research landscape.
Scalar field dark matter is a prominent option that is being explored with
precision instruments, such as atomic clocks and optical cavities. Here we
report on the first direct search for scalar field dark matter utilising a
gravitational-wave detector, which operates beyond the quantum shot-noise
limit. We set new upper limits for the coupling constants of scalar field dark
matter as a function of its mass, by excluding the presence of signals that
would be produced through the direct coupling of this dark matter to the
beamsplitter of the GEO600 interferometer. The new constraints improve upon
bounds from previous direct searches by more than six orders of magnitude, and
are in some cases more stringent than limits obtained in tests of the
equivalence principle by up to four orders of magnitude. Our work demonstrates
that scalar field dark matter can be probed or constrained with direct searches
using gravitational-wave detectors, and highlights the potential of
quantum-enhanced interferometry for dark matter detection
Characterization and evasion of backscattered light in the squeezed-light enhanced gravitational wave interferometer GEO 600
Squeezed light is injected into the dark port of gravitational wave interferometers, in order to reduce the quantum noise. A fraction of the interferometer output light can reach the OPO due to sub-optimal isolation of the squeezing injection path. This backscattered light interacts with squeezed light generation process, introducing additional measurement noise. We present a theoretical description of the noise coupling mechanism and we prove the model with experimental results. We propose a control scheme to achieve a de-amplification of the backscattered light inside the OPO with a consequent reduction of the noise caused by it. The scheme was implemented at the GEOâ600 detector and has proven to be crucial in maintaining a good level of quantum noise reduction of the interferometer for high parametric gain of the OPO. In particular, the mitigation of the backscattered light noise helped in reaching 6â
dB of quantum noise reduction [Phys. Rev. Lett. 126, 041102 (2021) [CrossRef] ]. We show that the impact of backscattered-light-induced noise on the squeezing performance is phenomenologically equivalent to increased phase noise of the squeezing angle control. The results discussed in this paper provide a way for a more accurate estimation of the residual phase noise of the squeezed light field. Finally, the knowledge of the backscattered light noise coupling mechanism is a useful tool to inform the design of the squeezing injection path in terms of path stability and optical isolation
Search for intermediate mass black hole binaries in the first observing run of Advanced LIGO
International audienceDuring their first observational run, the two Advanced LIGO detectors attained an unprecedented sensitivity, resulting in the first direct detections of gravitational-wave signals produced by stellar-mass binary black hole systems. This paper reports on an all-sky search for gravitational waves (GWs) from merging intermediate mass black hole binaries (IMBHBs). The combined results from two independent search techniques were used in this study: the first employs a matched-filter algorithm that uses a bank of filters covering the GW signal parameter space, while the second is a generic search for GW transients (bursts). No GWs from IMBHBs were detected; therefore, we constrain the rate of several classes of IMBHB mergers. The most stringent limit is obtained for black holes of individual mass 100ââMâ, with spins aligned with the binary orbital angular momentum. For such systems, the merger rate is constrained to be less than 0.93ââGpcâ3âyrâ1 in comoving units at the 90%Â confidence level, an improvement of nearly 2 orders of magnitude over previous upper limits