Published July 2, 2020 | Version Supplemental Material + Submitted
Journal Article Open

Quantum correlations between light and the kilogram-mass mirrors of LIGO

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Abstract

The measurement of minuscule forces and displacements with ever greater precision is inhibited by the Heisenberg uncertainty principle, which imposes a limit to the precision with which the position of an object can be measured continuously, known as the standard quantum limit. When light is used as the probe, the standard quantum limit arises from the balance between the uncertainties of the photon radiation pressure applied to the object and of the photon number in the photoelectric detection. The only way to surpass the standard quantum limit is by introducing correlations between the position/momentum uncertainty of the object and the photon number/phase uncertainty of the light that it reflects. Here we confirm experimentally the theoretical prediction that this type of quantum correlation is naturally produced in the Laser Interferometer Gravitational-wave Observatory (LIGO). We characterize and compare noise spectra taken without squeezing and with squeezed vacuum states injected at varying quadrature angles. After subtracting classical noise, our measurements show that the quantum mechanical uncertainties in the phases of the 200-kilowatt laser beams and in the positions of the 40-kilogram mirrors of the Advanced LIGO detectors yield a joint quantum uncertainty that is a factor of 1.4 (3 decibels) below the standard quantum limit. We anticipate that the use of quantum correlations will improve not only the observation of gravitational waves, but also more broadly future quantum noise-limited measurements.

Additional Information

© 2020 The Author(s), under exclusive licence to Springer Nature Limited. Received 03 February 2020; Accepted 04 May 2020; Published 01 July 2020. LIGO was constructed by the California Institute of Technology and the Massachusetts Institute of Technology with funding from the National Science Foundation, and operates under Cooperative Agreement number PHY-1764464. Advanced LIGO was built under grant number PHY-0823459. The authors gratefully acknowledge the support of the Australian Research Council under the ARC Centre of Excellence for Gravitational Wave Discovery grant number CE170100004, Linkage Infrastructure, Equipment and Facilities grant number LE170100217 and Discovery Early Career Award number DE190100437; the National Science Foundation Graduate Research Fellowship under grant number 1122374; the Science and Technology Facilities Council of the United Kingdom; and the LIGO Scientific Collaboration Fellows programme. Data availability: Source data for Figs. 2, 3, Extended Data Figs. 1–3 and other data pertaining to this study are available from the corresponding authors upon reasonable request. Author Contributions: The measurements presented in this paper were performed with the 4-km detector at the LIGO Livingston Observatory using a novel squeezed light source. Haocun Yu performed all of the measurements. Haocun Yu and L.M. carried out the analysis of the data. M. Tse, Haocun Yu and N.K. built and commissioned the squeezed-light sources. L.B. led the squeezed-light upgrade of the LIGO detectors, involving contributions from a large number of people within the LIGO Laboratory, the Australian National University and other members of the LIGO Scientific Collaboration. N.M. led the experimental campaign to measure sub-SQL quantum noise in the Advanced LIGO detector. Haocun Yu, L.M., M. Tse, L.B. and N.M. contributed directly to the preparation of the manuscript. The authors declare no competing interests.

Attached Files

Submitted - 2002.01519.pdf

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Supplemental Material - 41586_2020_2420_Tab1_ESM.jpg

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Additional details

Additional titles

Alternative title
Quantum correlations between the light and kilogram-mass mirrors of LIGO

Identifiers

Eprint ID
102777
Resolver ID
CaltechAUTHORS:20200424-112847161

Related works

Funding

NSF
PHY-1764464
NSF
PHY-0823459
Australian Research Council
CE170100004
Australian Research Council
LE170100217
Australian Research Council
DE190100437
NSF Graduate Research Fellowship
DGE-1122374
Science and Technology Facilities Council (STFC)
LIGO Scientific Collaboration Fellows

Dates

Created
2020-04-24
Created from EPrint's datestamp field
Updated
2022-10-27
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