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  • Featured in Physics
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Broadband Quantum Enhancement of the LIGO Detectors with Frequency-Dependent Squeezing

D. Ganapathy1,*, W. Jia1,*, M. Nakano2,*, V. Xu1,*, N. Aritomi3, T. Cullen4, N. Kijbunchoo5, S. E. Dwyer3, A. Mullavey2 et al. (LIGO O4 Detector Collaboration)

A. Mullavey2, L. McCuller4, R. Abbott4, I. Abouelfettouh3, R. X. Adhikari4, A. Ananyeva4, S. Appert4, K. Arai4, S. M. Aston2, M. Ball6, S. W. Ballmer7, D. Barker3, L. Barsotti1,†, B. K. Berger9, J. Betzwieser2, D. Bhattacharjee8, G. Billingsley4, S. Biscans4,1, N. Bode10,11, E. Bonilla9, V. Bossilkov2, A. Branch2, A. F. Brooks4, D. D. Brown12, J. Bryant13, C. Cahillane7, H. Cao14, E. Capote7, F. Clara3, J. Collins2, C. M. Compton3, R. Cottingham2, D. C. Coyne4, R. Crouch3, J. Csizmazia3, L. P. Dartez3, N. Demos1, E. Dohmen3, J. C. Driggers3, A. Effler2, A. Ejlli15, T. Etzel4, M. Evans1, J. Feicht4, R. Frey6, W. Frischhertz2, P. Fritschel1, V. V. Frolov2, P. Fulda16, M. Fyffe2, B. Gateley3, J. A. Giaime17,2, K. D. Giardina2, J. Glanzer17, E. Goetz18, R. Goetz16, A. W. Goodwin-Jones19, S. Gras1, C. Gray3, D. Griffith4, H. Grote15, T. Guidry3, E. D. Hall1, J. Hanks3, J. Hanson2, M. C. Heintze2, A. F. Helmling-Cornell6, N. A. Holland20, D. Hoyland13, H. Y. Huang21, Y. Inoue21, A. L. James15, A. Jennings3, S. Karat4, S. Karki22, M. Kasprzack4, K. Kawabe3, P. J. King3, J. S. Kissel3, K. Komori1, A. Kontos23, R. Kumar3, K. Kuns1, M. Landry3, B. Lantz9, M. Laxen2, K. Lee24, M. Lesovsky4, F. Llamas25, M. Lormand2, H. A. Loughlin1, R. Macas26, M. MacInnis1, C. N. Makarem4, B. Mannix6, G. L. Mansell7,1, R. M. Martin27, K. Mason1, F. Matichard4, N. Mavalvala1, N. Maxwell3, G. McCarrol2, R. McCarthy3, D. E. McClelland28, S. McCormick2, T. McRae28, F. Mera3, E. L. Merilh2, F. Meylahn10,11, R. Mittleman1, D. Moraru3, G. Moreno3, T. J. N. Nelson2, A. Neunzert3, J. Notte27, J. Oberling3, T. O’Hanlon2, C. Osthelder4, D. J. Ottaway12, H. Overmier2, W. Parker2, A. Pele4, H. Pham2, M. Pirello3, V. Quetschke25, K. E. Ramirez2, J. Reyes27, J. W. Richardson14, M. Robinson3, J. G. Rollins4, C. L. Romel3, J. H. Romie2, M. P. Ross29, K. Ryan3, T. Sadecki3, A. Sanchez3, E. J. Sanchez4, L. E. Sanchez4, R. L. Savage3, D. Schaetzl4, M. G. Schiworski12, R. Schnabel30, R. M. S. Schofield6, E. Schwartz15, D. Sellers2, T. Shaffer3, R. W. Short3, D. Sigg3, B. J. J. Slagmolen28, C. Soike3, S. Soni1, V. Srivastava7, L. Sun28, D. B. Tanner16, M. Thomas2, P. Thomas3, K. A. Thorne2, C. I. Torrie4, G. Traylor2, A. S. Ubhi13, G. Vajente4, J. Vanosky4, A. Vecchio13, P. J. Veitch12, A. M. Vibhute3, E. R. G. von Reis3, J. Warner3, B. Weaver3, R. Weiss1, C. Whittle1, B. Willke10,11, C. C. Wipf4, H. Yamamoto4, L. Zhang4, and M. E. Zucker1,4 (LIGO O4 Detector Collaboration)

  • 1LIGO Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
  • 2LIGO Livingston Observatory, Livingston, Louisiana 70754, USA
  • 3LIGO Hanford Observatory, Richland, Washington 99352, USA
  • 4LIGO Laboratory, California Institute of Technology, Pasadena, California 91125, USA
  • 5OzGrav, School of Physical Sciences, University of Adelaide, Adelaide 5005, Australia
  • 6University of Oregon, Eugene, Oregon 97403, USA
  • 7Syracuse University, Syracuse, New York 13244, USA
  • 8Kenyon College, Gambier, Ohio 43022, USA
  • 9Stanford University, Stanford, California 94305, USA
  • 10Max Planck Institute for Gravitational Physics (Albert Einstein Institute), D-30167 Hannover, Germany
  • 11Leibniz Universität Hannover, D-30167 Hannover, Germany
  • 12OzGrav, University of Adelaide, Adelaide, South Australia 5005, Australia
  • 13University of Birmingham, Birmingham B15 2TT, United Kingdom
  • 14University of California, Riverside, Riverside, California 92521, USA
  • 15Cardiff University, Cardiff CF24 3AA, United Kingdom
  • 16University of Florida, Gainesville, Florida 32611, USA
  • 17Louisiana State University, Baton Rouge, Louisiana 70803, USA
  • 18University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
  • 19OzGrav, University of Western Australia, Crawley, Western Australia 6009, Australia
  • 20Vrije Universiteit Amsterdam, 1081 HV, Amsterdam, Netherlands
  • 21National Central University, Taoyuan City 320317, Taiwan
  • 22Missouri University of Science and Technology, Rolla, Missouri 65409, USA
  • 23Bard College, Annandale-On-Hudson, New York 12504, USA
  • 24Sungkyunkwan University, Seoul 03063, Republic of Korea
  • 25The University of Texas Rio Grande Valley, Brownsville, Texas 78520, USA
  • 26University of Portsmouth, Portsmouth, PO1 3FX, United Kingdom
  • 27Montclair State University, Montclair, New Jersey 07043, USA
  • 28OzGrav, Australian National University, Canberra, Australian Capital Territory 0200, Australia
  • 29University of Washington, Seattle, Washington 98195, USA
  • 30Universität Hamburg, D-22761 Hamburg, Germany

  • *These authors contributed equally to this work.
  • †lisabar@ligo.mit.edu
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Phys. Rev. X 13, 041021 – Published 30 October, 2023

DOI: https://doi.org/10.1103/PhysRevX.13.041021

Abstract

Quantum noise imposes a fundamental limitation on the sensitivity of interferometric gravitational-wave detectors like LIGO, manifesting as shot noise and quantum radiation pressure noise. Here, we present the first realization of frequency-dependent squeezing in full-scale gravitational-wave detectors, resulting in the reduction of both shot noise and quantum radiation pressure noise, with broadband detector enhancement from tens of hertz to several kilohertz. In the LIGO Hanford detector, squeezing reduced the detector noise amplitude by a factor of 1.6 (4.0 dB) near 1 kHz; in the Livingston detector, the noise reduction was a factor of 1.9 (5.8 dB). These improvements directly impact LIGO’s scientific output for high-frequency sources (e.g., binary neutron star postmerger physics). The improved low-frequency sensitivity, which boosted the detector range by 15%–18% with respect to no squeezing, corresponds to an increase in the astrophysical detection rate of up to 65%. Frequency-dependent squeezing was enabled by the addition of a 300-meter-long filter cavity to each detector as part of the LIGO A+ upgrade.

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Research News

Quieting Noise in Gravitational-Wave Detectors

Published 30 October, 2023

The LIGO Scientific Collaboration has demonstrated a noise-squeezing technique for the entire range of gravitational frequencies LIGO can detect—a feat that could boost the detection rate of black hole mergers by up to 65%.

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Popular Summary

The sensitivity of interferometric gravitational-wave detectors like LIGO is ultimately limited by quantum fluctuations of electromagnetic fields that create noise on the readout photodetectors. One way to mitigate this quantum noise is to employ “squeezed vacuum states.” This is where the electromagnetic ground state is manipulated so that the quantum uncertainty in either the phase or amplitude is reduced at the expense of the other. Here, as part of a detector upgrade, we present the first implementation of “frequency-dependent squeezing” at LIGO. The subsequent noise reduction boosts the detector range by up to 18%, corresponding to an increase in detection rate of up to 65%.

In their third observing run, LIGO and other gravitational-wave detectors employed frequency-independent squeezing, which reduced the shot noise from quantum fluctuations, but at the expense of increased noise from radiation pressure. To circumvent this, we built a 300-meter-long optical cavity (called a “filter cavity”) at both LIGO sites to enable frequency-dependent squeezing. The squeezed vacuum states are reflected off this long cavity before injection into the interferometer, enabling a frequency-dependent rotation of the squeezed state.

Two decades after frequency-dependent squeezing was initially proposed, this latest result fully establishes it as a new fundamental technology for current and future gravitational-wave detectors.

Article Text

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Phys. Rev. X 13, 041021– Published 30 October, 2023
  • Received 15 April 2023
  • Revised 22 July 2023
  • Accepted 6 September 2023
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