The international network of gravitational-wave detectors has pushed the precision of its measurements so far that it is limited by the quantum nature of light itself. The laser beam used to measure the differential arm length in GEO600 is not truly continuous, but consists, as any light beam, of a large number of light particles (photons). The very nature of light itself implies that these photons are not arranged like a string of pearls but are travelling in irregular groups, and it is this grouping that creates noise in the gravitational wave measurement.

In 2010 GEO600 was the first gravitational wave detector to apply squeezed light injection to reduce this quantum noise and to this day GEO600 holds the world record in duration and strength of squeezed light used. The squeezed light source was developed and built at the Albert Einstein Institute, and currently the optimal application of squeezed light injection is a topic of ongoing research at GEO600, including:

  • the development of an automatic alignment system for squeezed light,
  • the development of a new control signal for squeezing angle detection, and
  • automated locking of the squeezed light source.

With all these techniques combined, the first long-term application of squeezed light at a GW detector has been achieved. Squeezing can typically be applied for more than 90% of the time, and we could show that squeezing is compatible with a low glitch rate of the h-channel.

GEO600 reaches 6 dB of squeezing
German-British instrument mitigates quantum noise effects better than any gravitational-wave detector before more
New squeezing record at GEO600

New squeezing record at GEO600

December 13, 2018
The German-British gravitational-wave detector makes a key step towards third-generation observatories like the Einstein Telescope more
Squeezed laser will bring gravitational waves to the light of day
A quantum phenomenon allows detectors which sense oscillations of space-time to measure with 50 percent more accuracy. more

The Virgo squeezer

The Virgo instrument has received a squeezer system based on the GEO600 design in 2018. The squeezer was built at the Max Planck Institute for Gravitational Phyics (Albert Einstein Institute) in Hannover.

Squeezed Light Success at Virgo
The gravitational-wave observatory near Pisa listens deeper into the cosmos with technology from Hanover more
Cutting-edge technology from Hannover for the Virgo gravitational-wave detector in Italy
Squeezed-light source developed at the Albert Einstein Institute to make Virgo even more sensitive to gravitational waves more

Relevant publications

J. Lough et al.
First demonstration of 6 dB quantum noise reduction in a kilometer scale gravitational wave observatory
Phys. Rev. Lett. 126, 041102 (2021)
E. Schreiber, K. L. Dooley, H. Vahlbruch, C. Affeldt, A. Bisht, J. R. Leong, J. Lough, M. Prijatelj, J. Slutsky, M. Was, H. Wittel, K. Danzmann, and H. Grote
Alignment sensing and control for squeezed vacuum states of light
Optics Express Vol. 24, Issue 1 (2016)
K. L. Dooley, E. Schreiber, H. Vahlbruch, C. Affeldt, J. R. Leong, H. Wittel, and H. Grote
Phase control of squeezed vacuum states of light in gravitational wave detectors
Optics Express Vol. 23, Issue 7 (2015)
H. Grote, K. Danzmann, K.L. Dooley, R. Schnabel, J. Slutsky, and H. Vahlbruch
First Long-Term Application of Squeezed States of Light in a Gravitational-Wave Observatory
Phys. Rev. Lett. 110, 181101 (2013)
The LIGO Scientific Collaboration
A gravitational wave observatory operating beyond the quantum shot-noise limit
Nature Physics volume 7 (2011)
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