The possible design of a quantum nondemolition gravitational-wave detector based on the speed meter principle is considered with respect to optical losses. A detailed analysis of a speed meter interferometer is performed and the ultimate sensitivity that can be achieved is calculated. It is shown that unlike with the position meter signal recycling can hardly be implemented in speed meter topology to replace the arm cavities, as is done in signal-recycled detectors such as GEO 600. It is also shown that a speed meter can beat the standard quantum limit by a factor of $\sim 3$ in a relatively wide frequency band, and by a factor of $\sim 10$ in a narrow band. For wideband detection the speed meter requires a quite reasonable amount of circulating power $\sim 1\mathrm{MW}.$ The advantage of the considered scheme is that it can be implemented with minimal changes in the current optical layout of the LIGO interferometer.

• Received 8 December 2003

DOI:https://doi.org/10.1103/PhysRevD.69.102003