  The most efficient approach to laser interferometric force sensing to date
uses monochromatic carrier light with its signal sideband spectrum in a
squeezed vacuum state. Quantum decoherence, i.e. mixing with an ordinary vacuum
state due to optical losses, is the main sensitivity limit. In this work, we
present both theoretical and experimental evidence that quantum decoherence in
high-precision laser interferometric force sensors enhanced with optical
cavities and squeezed light injection can be mitigated by a quantum squeeze
operation inside the sensor's cavity. Our experiment shows an enhanced
measurement sensitivity that is independent of the optical readout loss in a
wide range. Our results pave the way for quantum improvements in scenarios
where high decoherence previously precluded the use of squeezed light. Our
results hold significant potential for advancing the field of quantum sensors
and enabling new experimental approaches in high-precision measurement
technology.
