The quantum locking technique, which uses additional short low-loss sub-cavities, is effective in reducing quantum noise in space gravitational wave antenna DECIGO. However, the quantum noise of the main interferometer depends on the control systems in the sub-cavities. Here we demonstrate a new method to optimize the quantum noise independently of the feedback gain by completing the square in the quantum locking system. We successfully demonstrate in simulations that this method is effective in optimizing the homodyne angle to the best quantum-noise-limited sensitivity.
@article{arxiv.2003.13202,
title = {Optimization of quantum noise by completing the square of multiple interferometer outputs in quantum locking for gravitational wave detectors},
author = {Rika Yamada and Yutaro Enomoto and Atsushi Nishizawa and Koji Nagano and Sachiko Kuroyanagi and Keiko Kokeyama and Kentaro Komori and Yuta Michimura and Takeo Naito and Izumi Watanabe and Taigen Morimoto and Masaki Ando and Akira Furusawa and Seiji Kawamura},
journal= {arXiv preprint arXiv:2003.13202},
year = {2020}
}