521 research outputs found
First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data
Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of
continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a
fully coherent search, based on matched filtering, which uses the position and rotational parameters
obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto-
noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch
between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have
been developed, allowing a fully coherent search for gravitational waves from known pulsars over a
fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of
11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial
outliers, further studies show no significant evidence for the presence of a gravitational wave signal.
Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of
the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for
the first time. For an additional 3 targets, the median upper limit across the search bands is below the
spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried
out so far
Quantum correlation measurements in interferometric gravitational-wave detectors
Quantum fluctuations in the phase and amplitude quadratures of light set limitations on the sensitivity of modern optical instruments. The sensitivity of the interferometric gravitational-wave detectors, such as the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), is limited by quantum shot noise, quantum radiation pressure noise, and a set of classical noises. We show how the quantum properties of light can be used to distinguish these noises using correlation techniques. Particularly, in the first part of the paper we show estimations of the coating thermal noise and gas phase noise, hidden below the quantum shot noise in the Advanced LIGO sensitivity curve. We also make projections on the observatory sensitivity during the next science runs. In the second part of the paper we discuss the correlation technique that reveals the quantum radiation pressure noise from the background of classical noises and shot noise. We apply this technique to the Advanced LIGO data, collected during the first science run, and experimentally estimate the quantum correlations and quantum radiation pressure noise in the interferometer.National Science Foundation (U.S.)Kavli Foundation (Kavli Foundation
Point absorbers in Advanced LIGO
Small, highly absorbing points are randomly present on the surfaces of the main interferometer optics in Advanced LIGO. The resulting nanometer scale thermo-elastic deformations and substrate lenses from these micron-scale absorbers significantly reduce the sensitivity of the interferometer directly though a reduction in the power-recycling gain and indirect interactions with the feedback control system. We review the expected surface deformation from point absorbers and provide a pedagogical description of the impact on power buildup in second generation gravitational wave detectors (dual-recycled Fabry–Perot Michelson interferometers). This analysis predicts that the power-dependent reduction in interferometer performance will significantly degrade maximum stored power by up to 50% and, hence, limit GW sensitivity, but it suggests system wide corrections that can be implemented in current and future GW detectors. This is particularly pressing given that future GW detectors call for an order of magnitude more stored power than currently used in Advanced LIGO in Observing Run 3. We briefly review strategies to mitigate the effects of point absorbers in current and future GW wave detectors to maximize the success of these enterprises
Quantum-enhanced advanced LIGO detectors in the era of gravitational-wave astronomy
The Laser Interferometer Gravitational Wave Observatory (LIGO) has been directly detecting gravitational waves from compact binary mergers since 2015. We report on the first use of squeezed vacuum states in the direct measurement of gravitational waves with the Advanced LIGO H1 and L1 detectors. This achievement is the culmination of decades of research to implement squeezed states in gravitational-wave detectors. During the ongoing O3 observation run, squeezed states are improving the sensitivity of the LIGO interferometers to signals above 50 Hz by up to 3 dB, thereby increasing the expected detection rate by 40% (H1) and 50% (L1)
Approaching the motional ground state of a 10 kg object
The motion of a mechanical object -- even a human-sized object -- should be
governed by the rules of quantum mechanics. Coaxing them into a quantum state
is, however, difficult: the thermal environment masks any quantum signature of
the object's motion. Indeed, the thermal environment also masks effects of
proposed modifications of quantum mechanics at large mass scales. We prepare
the center-of-mass motion of a 10 kg mechanical oscillator in a state with an
average phonon occupation of 10.8. The reduction in temperature, from room
temperature to 77 nK, is commensurate with an 11 orders-of-magnitude
suppression of quantum back-action by feedback -- and a 13 orders-of-magnitude
increase in the mass of an object prepared close to its motional ground state.
This begets the possibility of probing gravity on massive quantum systems.Comment: published version containing minor change
Quantum correlations between the light and kilogram-mass mirrors of LIGO
Measurement of minuscule forces and displacements with ever greater precision
encounters a limit imposed by a pillar of quantum mechanics: the Heisenberg
uncertainty principle. A limit to the precision with which the position of an
object can be measured continuously is known as the standard quantum limit
(SQL). When light is used as the probe, the SQL arises from the balance between
the uncertainties of photon radiation pressure imposed on the object and of the
photon number in the photoelectric detection. The only possibility surpassing
the SQL is via correlations within the position/momentum uncertainty of the
object and the photon number/phase uncertainty of the light it reflects. Here,
we experimentally prove the theoretical prediction that this type of quantum
correlation is naturally produced in the Laser Interferometer
Gravitational-wave Observatory (LIGO). Our measurements show that the quantum
mechanical uncertainties in the phases of the 200 kW laser beams and in the
positions of the 40 kg mirrors of the Advanced LIGO detectors yield a joint
quantum uncertainty a factor of 1.4 (3dB) below the SQL. We anticipate that
quantum correlations will not only improve gravitational wave (GW)
observatories but all types of measurements in future
Sensitivity and performance of the Advanced LIGO detectors in the third observing run
On April 1st, 2019, the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO), joined by the Advanced Virgo detector, began the third observing run, a year-long dedicated search for gravitational radiation. The LIGO detectors have achieved a higher duty cycle and greater sensitivity to gravitational waves than ever before, with LIGO Hanford achieving angle-averaged sensitivity to binary neutron star coalescences to a distance of 111 Mpc, and LIGO Livingston to 134 Mpc with duty factors of 74.6% and 77.0% respectively. The improvement in sensitivity and stability is a result of several upgrades to the detectors, including doubled intracavity power, the addition of an in-vacuum optical parametric oscillator for squeezed-light injection, replacement of core optics and end reaction masses, and installation of acoustic mode dampers. This paper explores the purposes behind these upgrades, and explains to the best of our knowledge the noise currently limiting the sensitivity of each detector
Environmental Noise in Advanced LIGO Detectors
The sensitivity of the Advanced LIGO detectors to gravitational waves can be
affected by environmental disturbances external to the detectors themselves.
Since the transition from the former initial LIGO phase, many improvements have
been made to the equipment and techniques used to investigate these
environmental effects. These methods have aided in tracking down and mitigating
noise sources throughout the first three observing runs of the advanced
detector era, keeping the ambient contribution of environmental noise below the
background noise levels of the detectors. In this paper we describe the methods
used and how they have led to the mitigation of noise sources, the role that
environmental monitoring has played in the validation of gravitational wave
events, and plans for future observing runs
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