Squeezed states and the quantum noise of measurement

Abstract
The reduction of quantum noise in homodyne experiments on squeezed radiation is explained as the reduction of quantum noise of measurement at the modulated frequencies. The quantum noise measured by the spectrum analyzer is given by the Fourier transform of the intensity fluctuations correlation function. The zero line which represents the ‘‘quantum limit’’ is the quantum noise of measurement of the local oscillator radiation, and it is proportional to the square root of the laser intensity.