Distillation of Squeezing from Non-Gaussian Quantum States

We show that single copy distillation of squeezing from continuous variable non-Gaussian states is possible using linear optics and conditional homodyne detection. A specific non-Gaussian noise source, corresponding to a random linear displacement, is investigated experimentally. Conditioning the signal on a tap measurement, we observe probabilistic recovery of squeezing.

Figure 1

Schematic of the experimental setup for the generation, distillation, and verification of non-Gaussian squeezed states.

Figure 2

Experimentally measured marginal distributions, centered at zero for convenience, outlining the distillation of a squeezed state from a non-Gaussian mixture of squeezed states: (a) tap measurement $p_t$, (b) signal measurement $x_s$. Inset: phase space representation of the mixed state and the projection axes used in the measurements.

Figure 3

Experimentally and theoretically distilled squeezing (left) and success probability (right) as a function of postselection threshold for two displacements. The threshold is given relative the center of the marginal distributions.

Figure 4

Distilled variance (left axis) and success probability (right axis) as a function of the quadrature angle relative to the squeezed quadrature (defined in Fig. 2) in the tap measurement for a postselection threshold of 5.3 shot noise units.

Figure 5

Density plots of the Wigner function distributions for (a) the non-Gaussian mixed state and (b) the Wigner function of the corresponding distilled state. The Wigner function was reconstructed using the inverse Radon transform [16]. The shift to the right reflects the postselection process as well as the renormalization of the distilled data. To aid visualization the plots have been vertically rescaled by a factor of two.