  Some next-generation gravitational-wave detectors, such as the American
Advanced LIGO project and the Japanese LCGT project, plan to use power recycled
resonant sideband extraction (RSE) interferometers for their interferometer's
optical configuration. A power recycled zero-detuning (PRZD) RSE
interferometer, which is the default design for LCGT, has five main length
degrees of freedom that need to be controlled in order to operate a
gravitational-wave detector. This task is expected to be very challenging
because of the complexity of optical configuration. A new control scheme for a
PRZD RSE interferometer has been developed and tested with a prototype
interferometer. The PRZD RSE interferometer was successfully locked with the
control scheme. It is the first experimental demonstration of a PRZD RSE
interferometer with suspended test masses. The result serves as an important
step for the operation of LCGT.
