  Future interferometric gravitational wave detectors will make use of the
coupling between shot noise and radiation pressure noise that produces a
squeezed output for the quantum noise at the dark-port of the interferometer
allowing these interferometers to operate with a sensitivity that exceeds the
standard quantum limit at certain frequencies. The ability of the detector to
take advantage of this squeezed output state depends in part on the readout
system used. With the phase modulated laser input planned for these
interferometers the quantum-noise limited sensitivity is slightly better when
homodyne (rather than heterodyne) detection is used. We show that by modifying
the laser input spectrum for these interferometers, readout with heterodyne
detection can be made to have the same quantum-noise limited sensitivity as
readout with homodyne detection.
