Reduction of optimum light power with Heisenberg-limited photon-counting noise in interferometric gravitational-wave detectors

We study how the behavior of quantum noise, presenting the fundamental limi t on the sensitivity of interferometric gravitational-wave detectors, depen ds on properties of input states of light. We analyze the situation with sp ecially prepared nonclassical input states which reduce the photon-counting noise to the Heisenberg limit. This results in a great reduction of the op timum light power needed to achieve the standard quantum limit, compared to the usual configuration. (C) 1999 Published by Elsevier Science B.V. All r ights reserved.