Quantum Enhancement of LIGO beyond the Standard Quantum Limit
ORAL
Abstract
LIGO, a gravitational-wave detector, continuously measures the relative positions of four suspended 40-kg mirrors to observe spacetime modulations from cataclysmic astrophysical events. However, an optical measurement of position introduces momentum backaction which increases the uncertainty of subsequent position measurements. This momentum backaction associated with the position measurement gives rise to a limit the ultimate sensitivity with which individual photons can measure the position of a freely moving object, known as the standard quantum limit (SQL). The recently upgraded LIGO A+ detector injects backaction-evading squeezing light to leverage the quantum correlations between photons and massive 40 kilogram mirrors that breaks the SQL. Here, we present the first analysis of quantum noise in kilometer-scale gravitational wave detectors operating with frequency-dependent squeezing. We find that the LIGO interferometers surpass the SQL by up to 3 dB at 50 Hz while reducing quantum noise at nearly all astrophysical frequencies.
*The authors gratefully acknowledge the support of the United States National Science Founda- tion (NSF) for the construction and operation of the LIGO Laboratory and Advanced LIGO as well as the Science and Technology Facilities Council (STFC) of the United Kingdom, and the Max-Planck-Society (MPS) for support of the construction of Advanced LIGO. Ad- ditional support for Advanced LIGO was provided by the Australian Research Council. The authors acknowl- edge the LIGO Scientific Collaboration Fellows pro- gram for additional support. LIGO was constructed by the California Institute of Technology and Mas- sachusetts Institute of Technology with funding from the National Science Foundation, and operates under coop- erative agreement PHY-18671764464. Advanced LIGO was built under award PHY-18680823459. The A+ Upgrade to Advanced LIGO is supported by US NSF award PHY-1834382 and UK STFC award ST/S00246/1, with additional support from the Australian Research Council.
