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arXiv:1702.01029 · Light Science & Applications

A new quantum speed-meter interferometer: measuring speed to search for intermediate mass black holes

S. L. Danilishin, E. Knyazev, N. V. Voronchev, Farid Ya Khalili, Christian A. Graf, S. Steinlechner, J. Hennig, S. Hild

Published May 30, 2018• 40 citations
arXivHTMLPDF

Abstract

Abstract The recent discovery of gravitational waves (GW) by Advanced LIGO (Laser Interferometric Gravitational-wave Observatory) has impressively launched the novel field of gravitational astronomy and allowed us to glimpse exciting objects about which we could previously only speculate. Further sensitivity improvements at the low-frequency end of the detection band of future GW observatories must rely on quantum non-demolition (QND) methods to suppress fundamental quantum fluctuations of the light fields used to readout the GW signal. Here we present a novel concept of how to turn a conventional Michelson interferometer into a QND speed-meter interferometer with coherently suppressed quantum back-action noise. We use two orthogonal polarizations of light and an optical circulator to couple them. We carry out a detailed analysis of how imperfections and optical loss influence the achievable sensitivity. We find that the proposed configuration significantly enhances the low-frequency sensitivity and increases the observable event rate of binary black-hole coalescences in the range of $$10^2 - 10^3\,M_ \odot$$ 1 0 2 - 1 0 3 M ⊙ by a factor of up to ~300.

DOI
10.1038/s41377-018-0004-2

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Abstract The recent discovery of gravitational waves (GW) by Advanced LIGO (Laser Interferometric Gravitational-wave Observatory) has impressively launched the novel field of gravitational astronomy and allowed us to glimpse exciting objects about which we could previously only speculate. Further sensitivity improvements at the low-frequency end of the detection band of future GW observatories must rely on quantum non-demolition (QND) methods to suppress fundamental quantum fluctuations of the light fields used to readout the GW signal. Here we present a novel concept of how to turn a conventional Michelson interferometer into a QND speed-meter interferometer with coherently suppressed quantum back-action noise. We use two orthogonal polarizations of light and an optical circulator to couple them. We carry out a detailed analysis of how imperfections and optical loss influence the achievable sensitivity. We find that the proposed configuration significantly enhances the low-frequency sensitivity and increases the observable event rate of binary black-hole coalescences in the range of 102−103 M⊙10^2 - 10^3\,M_ \odot102−103M⊙​ 1 0 2 - 1 0 3 M ⊙ by a factor of up to ~300.
The 2015 seminal discovery of gravitational waves (GW) from the collision of the binary black holes has boosted interest to development of a more sensitive next generation gravitational-wave interferometers. As the current Advanced LIGO and Virgo detectors are limited by fundamental quantum fluctuations of light in the most of their detection band, the next generation of interferometers must use advanced quantum noise-mitigation methods and quantum non-demolition (QND) techniques to achieve the planned design sensitivity of 10 times better than the current detectors have. In this paper, we attempt to give an overview of some advanced quantum metrology techniques being considered as potential sensitivity boosters for the next generation GW detectors.
We propose a quantum teleportation-based speed meter for interferometric displacement sensing. The primary motivation is to transform a conventional position-sensing interferometer into a quantum non-demolition speed measurement device, without modifying its fundamental optical configuration. Two equivalent implementations are presented: an online approach that uses real-time displacement operation and an offline approach that relies on post-processing. Both implementations reduce quantum radiation pressure noise and surpass the standard quantum limit of measuring displacement, and they can be applied to a wide range of interferometer configurations. We discuss potential applications to gravitational-wave detectors, where our scheme enhances low-frequency sensitivity without requiring modifications to the core optics of a conventional Michelson interferometer (e.g., substrate or coating properties). This approach offers a new path to back-action evasion enabled by quantum entanglement.
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We propose a new implementation of a quantum speed meter QND measurement scheme. It employs two independent optical readouts of the interferometer test masses with different values of the bandwidths and of the optical circulating power, whose outputs have to be combined by an additional beamsplitter. Signals at the two outputs of the beamsplitter are proportional to the position and the velocity of the test masses, respectively. The influence of the position meter-like back action force associated with the position signal can be cancelled using the EPR approach by measuring the amplitude quadrature of the beamsplitter common output. • This is an article for the Special Issue in memory of V.B. Braginsky. • We propose a novel and arguably the simplest scheme of a speed meter interferometer. • Speed meters curb quantum noise at low frequencies, boosting the SNR for GW sources. • Combination of readouts of two detectors with distinct bandwidths yields speed signal. • No significant changes of the current GWD infrastructure is necessary for our scheme.
Quantum fluctuation of light limits the sensitivity of advanced laser interferometric gravitational-wave detectors. It is one of the principal obstacles on the way towards the next-generation gravitational-wave observatories. The envisioned significant improvement of the detector sensitivity requires using quantum non-demolition measurement and back-action evasion techniques, which allow us to circumvent the sensitivity limit imposed by the Heisenberg uncertainty principle. In our previous review article (Danilishin and Khalili in Living Rev Relativ 15:5, 2012 ), we laid down the basic principles of quantum measurement theory and provided the framework for analysing the quantum noise of interferometers. The scope of this paper is to review novel techniques for quantum noise suppression proposed in the recent years and put them in the same framework. Our delineation of interferometry schemes and topologies is intended as an aid in the process of selecting the design for the next-generation gravitational-wave observatories.
The double-pass interferometer scheme was proposed in Ref.\,[Light Sci. Appl. {\bf 7}, 11 (2018)] as the method of implementation of the quantum speed meter concept in future laser gravitational-wave (GW) detectors. Later it was shown in Ref.\,[Phys. Rev. D {\bf 110}, 062006 (2024)] that it allows to implement the new type of the optical spring that does not require detuning of the interferometer. Here we show that both these regimes can coexist, combining the speed meter type broadband sensitivity gain with the additional lows-frequency minimum in the quantum noise originated from the optical spring. We show that the location of this minimum can be varied without affecting the core optics of the interferometer, allowing to tune the quantum noise shape in real time to follow the ``chirp'' GW signals.