  The Standard Quantum Limit (SQL) in interferometric displacement measurement
imposes a restriction on the precision of the measurement due to its quantum
back-action noise. This limit can be surpassed over a broad frequency band by
injecting squeezed vacuum states with a frequency dependent (FD) quadrature
angle into the measurement system. Here, we demonstrate the generation of FD
squeezed vacuum states by utilizing Einstein-Podolsky-Rosen (EPR) entangled
states. The frequency dependence of the squeezed state can be tuned by
conditionally filtering the measurement once the two entangled fields are
detected. A stable control scheme for the method is demonstrated which can be
implemented in future gravitational-wave detectors to improve their
astronomical reach.
