Abstract

We propose a new implementation of a quantum speed meter QND measurement scheme. It employs two independent optical readouts of the interferometer test masses with different values of the bandwidths and of the optical circulating power, whose outputs have to be combined by an additional beamsplitter. Signals at the two outputs of the beamsplitter are proportional to the position and the velocity of the test masses, respectively. The influence of the position meter-like back action force associated with the position signal can be cancelled using the EPR approach by measuring the amplitude quadrature of the beamsplitter common output.

Highlights

  • The sensitivity of the modern laser-interferometric gravitational-wave (GW) detectors is limited by quantum fluctuations of the probing light over most of the sensitive frequency range

  • Suppression of the shot noise, which is necessary for achieving this goal, will require either an increase of the optical power circulating in the interferometer up to ∼ 1 MW, or the application of squeezed light states [7,8,9], and most probably a combination of both approaches will be used to maximise the sensitivity gain

  • Several implementations of the quantum speed meter concept suitable for the GW detectors were proposed, which can be divided into the following two categories: the first one relies on the ordinary Michelson interferometer topology of the contemporary GW detectors, but requires an additional long sloshing cavity [17, 18] and does not provide significant advantages in comparison with the filter cavities based topologies

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Summary

INTRODUCTION

The sensitivity of the modern laser-interferometric gravitational-wave (GW) detectors is limited by quantum fluctuations of the probing light over most of the sensitive frequency range. The basic idea of this concept is to measure the velocity of the probe mass(es) instead of their position In this case, the measurement noise and the back action noise spectral densities depend on the observation frequency in such a way that they can provide cancellation of each other by means of introducing a frequency-independent cross-correlation between them. Several implementations of the quantum speed meter concept suitable for the GW detectors were proposed, which can be divided into the following two categories: the first one relies on the ordinary Michelson interferometer topology of the contemporary GW detectors, but requires an additional long sloshing cavity [17, 18] and does not provide significant advantages in comparison with the filter cavities based topologies. In a broad band, long additional filter cavities are required [13]

Speed meter
IDEA OF THE EPR SPEED METER
PROSPECTS OF USE IN GW DETECTORS
Findings
DISCUSSION
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