  Quantum noise of the electromagnetic field is one of the limiting noise
sources in interferometric gravitational wave detectors. Shifting the spectrum
of squeezed vacuum states downwards into the acoustic band of gravitational
wave detectors is therefore of challenging demand to quantum optics
experiments. We demonstrate a system that produces nonclassical continuous
variable states of light that are squeezed at sideband frequencies below 100
kHz. A single optical parametric amplifier (OPA) is used in an optical noise
cancellation scheme providing squeezed vacuum states with coherent bright phase
modulation sidebands at higher frequencies. The system has been stably locked
for half an hour limited by thermal stability of our laboratory.
