quantum correlations PHOTONICS INSIGHTS injected into the interferometer, as the low-frequency sensitivity is not yet good enough to take advantage of it. Squeezing will be a key technology also for future detectors. Over the coming years, Virgo, LIGO, KAGRA, and third-generation detectors like the Einstein Telescope will continue improving the squeezing performances aiming to push squeezing levels up to 10 dB, corresponding to a noise reduction by a factor of three. To this purpose ongoing R & D efforts are focusing on reducing losses and adapting squeezing states to different detector configurations. Moreover, the community is investigating alternative quantum noise reduction techniques such as speed-meters, conditional frequency-dependent squeezing, white-light-cavity based schemes or quantum teleportation [ 10,11 ]. In conclusion, although quantum principles impose fundamental constraints on the sensitivity of gravitational wave detectors, they also enable strategies to circumvent the Heisenberg limit( of course without violating it!) through the implementation of squeezing techniques. What is truly fascinating is that by exploiting the principles of quantum mechanics at microscopic scales, we can
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