Quantum measurements with an amplitude-squeezed-light beam splitter

Quantum measurement of amplitude fluctuation is performed by the injection of 2.5-dB amplitude-squeezed light produced by a quantum-well laser into the dark port of a beam splitter as the meter wave. It is shown that the measurements satisfy the criteria of quantum nondemolition measurement. The measured transfer coefficient and the quantum-state preparation ability are 1.07 and 0.8, respectively.