Broadband quantum noise reduction in future long baseline gravitational-wave detectors via EPR entanglement

Abstract

Broadband quantum noise reduction can be achieved in gravitational wave detectors by injecting frequency dependent squeezed light into the the dark port of the interferometer. This frequency dependent squeezing can be generated by combining squeezed light with external filter cavities. However, in future long baseline interferometers (LBIs), the filter cavity required to achieve the broadband squeezing has a low bandwidthnecessitating a very long cavity to mitigate the issue from optical loss. It has been shown recently that by taking advantage of Einstein-Podolsky-Rosen (EPR) entanglement in the squeezed light source, the interferometer can simultaneously act as a detector and a filter cavity. This is an attractive broadband squeezing scheme for LBIs because the length requirement for the filter cavity is naturally satisfied by the length of the interferometer arms. In this paper we present a systematic way of finding the working points for this broadband squeezing scheme in LBIs. We also show that in LBIs, the EPR scheme achieves nearly perfect ellipse rotation as compared to 4km interferometers which have appreciable error around the intermediate frequency. Finally, we show that an approximation for the opto-mechanical coupling constant in the 4km case can break down for longer baselines. These results are applicable to future detectors such as the 10km Einstein Telescope and the 40km Cosmic Explorer.arXiv:1909.03603v1 [quant-ph]

Demonstration of interferometer enhancement through Einstein–Podolsky–Rosen entanglement

“…As pointed out in the proposal, the approach suffers from a 3 dB noise penalty on the initial squeezing and an increased sensitivity to optical loss, both of which are due to the measurement of an additional pair of sidebands. However, in light of the high additional costs for low-loss, narrow-linewidth filter cavities, the demonstrated broadband enhancement of interferometer sensitivity through EPR entanglement can still be a viable alternative 30 .…”

Nonlinearly induced entanglement in dissipatively coupled optomechanical system

“…Notably, the optomechanical system offers a versatile platform for studying photon-phonon entanglement, [15][16][17] thereby delving into fundamental theories and quantum information manipulation. [18,19] Optomechanical entanglement is investigated in both theoretical [20,21] and experimental [22][23][24] aspects. Recent attention has gravitated towards dissipative coupling optomechanical systems [25] in contrast to traditional dispersive coupling, [26] owing to their distinctive properties via optical dissipation modulation by mechanical displacement.…”