Squeezed-state generation from single-photon sources

We propose a conditional generation of quantum squeezing from realistic single-photon states. The proposed method does not require any coherent measurement projecting on a superposition of internal levels inside single-photon emitters. Interestingly, the squeezing can be generated despite a low single-photon efficiency of the emitters. The method can therefore substantially enlarge the set of existing sources of the squeezed states of electromagnetic radiation. For example, it can be used to produce squeezed ultraviolet radiation based on already available ultraviolet single-photon emitters.

Figure 1

Single-copy (left) and two-copy (right) nonuniversal squeezing generation vs success probability: the variance $V_S$ of generated squeezing for $\eta =0.3$ (dot-dashed bold) and for $\eta =0.5$ (full bold) and for $\eta =0.9$ (dashed bold) compared to vacuum noise (dotted).

Figure 2

Linear-optical interacted circuit implementation of the nonuniversal Gaussian squeezing generation from $N=2^n$ input single-photon states ${\rho }_1\left(\eta \right)$: beam splitters with transmittancy $T=0.5$ and homodyne detectors measuring coordinates ${\overline{x}}_i,i=1,...,n$, are used.

Figure 3

Multicopy nonuniversal squeezing generation from single-photon state. (Left) Numerical values of minimal variance $V_S$ for $\eta =1$ fitted by rational function compared to theoretical limits (dashed thin) as a function of $M=N/2$. For the numerical data, polynomial interpolation has been used to fit the results. (Right) Minimal variance for $N=4$ (full thin) and $N=8$ (full thick) for partially (single-layer) nonuniversal method compared to fully nonuniversal procedure with $N=4$ (dashed thin) and $N=8$ (dashed thick) initial states.

Figure 4

Two-copy recycling with projective measurement on superposition $\alpha |0\rangle +\gamma |2\rangle$. (Left) Minimal variance of squeezed quadrature (full thick) is compared to minimal squeezed quadrature variance extracted by two-copy recycling with homodyne (dashed thick) and heterodyne (full thin) detectors and to vacuum noise (dashed thin). (Right) Optimal values of coefficients $\alpha$ (full thick) and $\gamma$ (dashed thick) are compared to unity (dashed thin).