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

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**Quantum correlations between light and the kilogram-mass mirrors of LIGO.** / LIGO Scientific Collaboration; Yu, Haocun; McCuller, L.; Tse, M.; Kijbunchoo, N.; Barsotti, L.; Mavalvala, N.; Lundgren, Andrew; Mozzon, Simone; Nuttall, Laura.

Research output: Contribution to journal › Article › peer-review

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*Nature*, vol. 583, pp. 43-47. https://doi.org/10.1038/s41586-020-2420-8

### APA

*Nature*,

*583*, 43-47. https://doi.org/10.1038/s41586-020-2420-8

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TY - JOUR

T1 - Quantum correlations between light and the kilogram-mass mirrors of LIGO

AU - LIGO Scientific Collaboration

AU - Yu, Haocun

AU - McCuller, L.

AU - Tse, M.

AU - Kijbunchoo, N.

AU - Barsotti, L.

AU - Mavalvala, N.

AU - Lundgren, Andrew

AU - Mozzon, Simone

AU - Nuttall, Laura

PY - 2020/7/2

Y1 - 2020/7/2

N2 - 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 limit1,2,3,4. 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 reflects5. Here we confirm experimentally the theoretical prediction5 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.

AB - 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 limit1,2,3,4. 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 reflects5. Here we confirm experimentally the theoretical prediction5 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.

KW - RCUK

KW - STFC

U2 - 10.1038/s41586-020-2420-8

DO - 10.1038/s41586-020-2420-8

M3 - Article

VL - 583

SP - 43

EP - 47

JO - Nature

JF - Nature

SN - 1476-4687

ER -

ID: 21793674