LIGO Document P1700253-v1

Quantum back-action-evading gravitational wave detection in the negative mass reference frame

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P - Publications
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Recent report on observation of gravitational waves [B.Abbott et al, Phys. Rev. Lett. 116, 061102, 2016; B.Abbott et al, Phys. Rev. Lett. 116, 241103, 2016] has opened new horizons in cosmology and astrophysics. Gravitational wave detectors (GWD) such as LIGO and VIRGO are soon expected to be limited by the standard quantum limit (SQL) stemming from the balance between the measurement sensitivity and quantum back action. Recently a method to overcome the SQL for the measurement of motion by introducing a quantum reference frame in the form of an atomic spin oscillator has been demonstrated [C.B.Moeller et al, Nature 547, 191, 2017]. The method involves a joint measurement on the mechanical and spin systems, with the latter playing the role of a negative mass reference frame. Here we demonstrate how this novel approach can be used to overcome the SQL for the free mass, such as a mirror of a GWD. We present a general idea of the approach and provide the analysis of its experimental feasibility with realistic experimental parameters. We show that under realistic conditions the sensitivity of the GWD can be increased by \( 6 \) dB over the entire frequency band of interest. We also outline the ways to use the atomic system memory function for the benefit of GWD.
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