BROAD-BAND DETECTION OF SQUEEZED VACUUM - A SPECTRUM OF QUANTUM STATES

We demonstrate the simultaneous quantum state reconstruction of the sp ectral modes of the light field emitted by a continuous-wave degenerat e optical parametric amplifier. The scheme is based on broadband measu rement of the quantum fluctuations of the electric-field quadratures a nd subsequent Fourier decomposition into spectral intervals. Applying the standard reconstruction algorithms to each bandwidth-limited quant um trajectory, a ''spectrum'' of density matrices and Wigner functions is obtained. The recorded states show a smooth transition from the sq ueezed vacuum to a vacuum state. In the time domain we evaluated the f irst-order correlation function of the squeezed output field, showing good agreement with theory.