Abstract
The engineering of strongly squeezed vacuum states of light is a key technology for the reduction of quantum noise in gravitational wave detectors. We report on the observation of up to 12.0 dB squeezed vacuum states of light at the wavelength of 1064 nm in the frequency band from 10 Hz to 100 kHz. This is the strongest squeezing reported to date within this detection band. The squeezed states were generated in a half-monolithic, standing-wave cavity optical parametric amplifier, which was resonant for the fundamental and harmonic light fields. We chose appropriate reflectivities to obtain a significant reduction of the required pump power, which was 8.6 mW only. Our analysis revealed that the residual measurement phase noise was smaller than 3.5 mrad rms and that the squeezed light source provided up to 14 dB of squeezing for a downstream application. The experiment was electronically stabilized in all relevant degrees of freedom, demonstrating the applicability of the linear, doubly resonant cavity topology for current and future gravitational wave detectors.
Highlights
The potential of using squeezed states of light [1,2,3,4] to enhance measurement processes beyond their classical limit has been demonstrated, for example, in spectroscopy experiments [5], laser-based particle tracking of living cells [6], to generate entangled quantum states for quantum-dense metrology [7] or to establish universally secure quantum key distribution [8]
Our analysis revealed that the measured squeezing level corresponds to an equivalent squeezing factor of up to 14 dB available for the injection into a gravitational wave detector with only 3.5 mrad rms of phase noise attributed to the squeezed light source operated in air
The phase-locking loop (PLL) feedback was applied to Laser 2, actuating on the laser crystal temperature and piezo actuator with a bandwidth of 50 kHz. 1 mW of Laser 1 light was transmitted through a mode-cleaner ring cavity (MC1064) that provided spatio-temporal filtering of the beam to be used as the local oscillator (LO) for balanced homodyne detection (BHD)
Summary
The potential of using squeezed states of light [1,2,3,4] to enhance measurement processes beyond their classical limit has been demonstrated, for example, in spectroscopy experiments [5], laser-based particle tracking of living cells [6], to generate entangled quantum states for quantum-dense metrology [7] or to establish universally secure quantum key distribution [8]. The long term operation of a squeezing enhanced interferometer configuration has been demonstrated at GEO 600, where squeezed states have been injected continuously since 2010 [12, 13] Both the LIGO detectors and the Virgo detector are currently working on the integration of the squeezed light technique aiming for routine operation in the upcoming observation periods. Squeezing enhancement has become an integral part of the conceptual layout of planned third-generation detectors, such as the European Einstein Telescope [14] and the US-American Cosmic Explorer [15] For these future generation instruments the aim is to apply squeezed states of light and achieve a level of 10 dB non-classical noise reduction to reach their envisaged sensitivities. A prerequisite for such a sensitivity enhancement is a squeezed light source that provides strongly squeezed vacuum states of light at the expected gravitational wave signal frequencies ranging from 10 Hz to 10 kHz
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