  Precision measurements using traditional heterodyne readout suffer a 3dB
quantum noise penalty compared with homodyne readout. The extra noise is caused
by the quantum fluctuations in the image vacuum. We propose a two-carrier
gravitational-wave detector design that evades the 3dB quantum penalty of
heterodyne readout. We further propose a new way of realising
frequency-dependent squeezing utilising two-mode squeezing in our scheme. It
naturally achieves more precise audio frequency signal measurements with radio
frequency squeezing. In addition, the detector is compatible with other quantum
nondemolition techniques.

General Relativity and Quantum Cosmology;Instrumentation and Detectors