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Physics, Instrumentation and Detectors, physics.ins-det, Physics, Optics, physics.optics,Quantum Physics, quant-ph
Abstract:
Beam alignment is an important practical aspect of the application of
squeezed states of light. Misalignments in the detection of squeezed light
result in a reduction of the observable squeezing level. In the case of
squeezed vacuum fields that contain only very few photons, special measures
must be taken in order to sense and control the alignment of the essentially
dark beam. The GEO600 gravitational wave detector employs a squeezed vacuum
source to improve its detection sensitivity beyond the limits set by classical
quantum shot noise. Here, we present our design and implementation of an
alignment sensing and control scheme that ensures continuous optimal alignment
of the squeezed vacuum field at GEO 600 on long time scales in the presence of
free-swinging optics. This first demonstration of a squeezed light automatic
alignment system will be of particular interest for future long-term
applications of squeezed vacuum states of light.