Figure 1. Experimental setup.

Squeezed light is prepared and combined in 'Squeezers' with a piezoelectric transducer (PZT) controlling the phase between the two squeezed modes, locked in quadrature. Vacuum modes (vac) copropagate so that the beam exiting 'Squeezers' and entering 'Detection' contains eight measurable spatial modes. MPHD is used to measure the quadrature amplitudes of the beam in eight different regions, in 'Detection'. Local oscillator (LO) gives a reference to phase quadratures. A PC is used to calculate electronic gain functions G_n via the notion of 'Virtual networks'. The detected beam is then projected onto a basis of measured modes (see equation (1)). Inset: FM generation; half of the wave is phase retarded by half a wavelength, flipping the electric field amplitude.