88 research outputs found
Reduction of Classical Measurement Noise via Quantum-Dense Metrology
Quantum-dense metrology (QDM) constitutes a special case of quantum metrology
in which two orthogonal phase space projections of a signal are simultaneously
sensed beyond the shot noise limit. Previously it was shown that the additional
sensing channel that is provided by QDM contains information that can be used
to identify and to discard corrupted segments from the measurement data. Here,
we demonstrate a proof-of-principle experiment in which this information is
used for improving the sensitivity without discarding any measurement segments.
Our measurement reached sub-shot-noise performance although initially strong
classical noise polluted the data
Optical Absorption Measurements on Crystalline Silicon at 1550nm
Crystalline silicon is currently being discussed as test-mass material for
future generations of gravitational wave detectors that will operate at
cryogenic temperatures. We present optical absorption measurements on a
large-dimension sample of crystalline silicon at a wavelength of 1550nm at room
temperature. The absorption was measured in a monolithic cavity setup using the
photo-thermal self-phase modulation technique. The result for the absorption
coefficient of this float-zone sample with a specific resistivity of 11kOhm cm
was measured to be \alpha_A=(264 +/- 39)ppm/cm.Comment: 11 pages, 6 figures, 1 tabl
Strong Einstein-Podolsky-Rosen steering with unconditional entangled states
In 1935 Schr\"odinger introduced the terms entanglement and steering in the
context of the famous gedanken experiment discussed by Einstein, Podolsky, and
Rosen (EPR). Here, we report on a sixfold increase of the observed EPR-steering
effect as quantified by the Reid-criterion. We achieved an unprecedented low
conditional variance product of about 0.04 < 1, where 1 is the upper bound
below which steering is present. The steering effect was observed on an
unconditional two-mode-squeezed entangled state that contained a total vacuum
state contribution of less than 8%, including detection imperfections. Together
with the achieved high interference contrast between the entangled state and a
bright coherent laser field, our state is compatible with efficient
applications in high-power laser interferometers and fiber-based networks for
entanglement distribution.Comment: 5 pages, 3 figure
Mapping the optical absorption of a substrate-transferred crystalline AlGaAs coating at 1.5 µm
The sensitivity of 2nd and 3rd generations of interferometric gravitational wave detectors will be limited by thermal noise of the test-mass mirrors and highly reflective coatings. Recently developed crystalline coatings show a promising thermal noise reduction compared to presently used amorphous coatings. However, stringent requirements apply to the optical properties of the coatings as well. We have mapped the optical absorption of a crystalline AlGaAs coating which is optimized for high reflectivity for a wavelength of 1064nm. The absorption was measured at 1550nm where the coating stack transmits approximately 70% of the laser light. The measured absorption was lower than (30.2 +/- 11.1)ppm which is equivalent to (3.6 +/- 1.3)ppm for a coating stack that is highly reflective at 1530nm. While this is a very promising low absorption result for alternative low--loss coating materials, further work will be necessary to reach the requirements of <1ppm for future gravitational wave detectors.
Jessica Steinlechner, Iain W Martin, Angus Bell, Garrett Cole, Jim Hough, Steven Penn, Sheila Rowan, Sebastian Steinlechne
Quantum metrology with squeezed and entangled light for the detection of gravitational waves
[no abstract
Mitigating quantum decoherence in force sensors by internal squeezing
The most efficient approach to laser interferometric force sensing to date
uses monochromatic carrier light with its signal sideband spectrum in a
squeezed vacuum state. Quantum decoherence, i.e. mixing with an ordinary vacuum
state due to optical losses, is the main sensitivity limit. In this work, we
present both theoretical and experimental evidence that quantum decoherence in
high-precision laser interferometric force sensors enhanced with optical
cavities and squeezed light injection can be mitigated by a quantum squeeze
operation inside the sensor's cavity. Our experiment shows an enhanced
measurement sensitivity that is independent of the optical readout loss in a
wide range. Our results pave the way for quantum improvements in scenarios
where high decoherence previously precluded the use of squeezed light. Our
results hold significant potential for advancing the field of quantum sensors
and enabling new experimental approaches in high-precision measurement
technology
Demonstration of interferometer enhancement through EPR entanglement
The sensitivity of laser interferometers used for the detection of
gravitational waves (GWs) is limited by quantum noise of light. An improvement
is given by light with squeezed quantum uncertainties, as employed in the GW
detector GEO600 since 2010. To achieve simultaneous noise reduction at all
signal frequencies, however, the spectrum of squeezed states needs to be
processed by 100m-scale low-loss optical filter cavities in vacuum. Here, we
report on the proof-of-principle of an interferometer setup that achieves the
required processed squeezed spectrum by employing Einstein-Podolsky-Rosen (EPR)
entangled states. Applied to GW detectors, the cost-intensive cavities would
become obsolete, while the price to pay is a 3dB quantum penalty
Fundamental sensitivity limit of lossy cavity-enhanced interferometers with external and internal squeezing
Quantum optical sensors are ubiquitous in various fields of research, from
biological or medical sensors to large-scale experiments searching for dark
matter or gravitational waves. Gravitational-wave detectors have been very
successful in implementing cavities and quantum squeezed light for enhancing
sensitivity to signals from black hole or neutron star mergers. However, the
sensitivity to weak forces is limited by available energy and optical
decoherence in the system. Here, we derive the fundamental sensitivity limit of
cavity and squeezed-light enhanced interferometers with optical loss.This limit
is attained by the optimal use of an additional internal squeeze operation,
which allows to mitigate readout loss. We demonstrate the application of
internal squeezing to various scenarios and confirm that it indeed allows to
reach the best sensitivity in cavity and squeezed-light enhanced linear force
sensors. Our work establishes the groundwork for the future development of
optimal sensors in real-world scenarios where, up until now, the application of
squeezed light was curtailed by various sources of decoherence
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