Full quantum state reconstruction of symmetric two-mode squeezed thermal states via spectral homodyne detection and a state-balancing detector

We suggest and demonstrate a scheme to reconstruct the symmetric two-mode squeezed thermal states of spectral sideband modes from an optical parametric oscillator. The method is based on both a single homodyne detector and the error signal from the active stabilization of the oscillator cavity. The measurement scheme has been successfully tested on different two-mode squeezed thermal states, ranging from uncorrelated coherent states to entangled states.