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Free keywords:
Quantum Physics, quant-ph
Abstract:
Currently, the German/British gravitational wave detector GEO600 is being
upgraded in course of the GEO-HF program. One part of this upgrade consists of
the integration of a squeezed light laser to nonclassically improve the
detection sensitivity at frequencies where the instrument is limited by shot
noise. This has been achieved recently [1]. The permanent employment of
squeezed light in gravitational wave observatories requires a long-term
stability of the generated squeezed state. In this paper, we discuss an
unwanted mechanism that can lead to a varying squeezing factor along with a
changing phase of the squeezed field. We present an extension of the
implemented coherent control scheme [2] that allowed an increase in the
long-term stability of the GEO600 squeezed light laser. With it, a quantum
noise reduction by more than 9 dB in the frequency band of 10 Hz - 10 kHz was
observed over up to 20 hours with a duty cycle of more than 99%.
