Time-gated Einstein-Podolsky-Rosen correlation

We experimentally demonstrate the creation and characterization of Einstein-Podolsky-Rosen (EPR) correlation between optical beams in a time-gated fashion. The correlated beams are created with two independent continuous-wave optical parametric oscillators and a half beam splitter. We define the temporal modes using a square temporal filter with duration $T$ and make time-resolved measurements on the generated state. We observe correlations between the relevant conjugate variables in the temporal mode which correspond to EPR correlation. Our scheme is extendable to continuous-variable quantum teleportation of a non-Gaussian state defined in the time domain such as a superposition of coherent states.

Figure 1

Schematic setup of the experiment. OPOs, subthreshold optical parametric oscillators; HBS, half beam splitter; PZTs, piezoelectric transducers; LOs, local oscillators; ADCs, analog-to-digital converters.

Figure 2

Calculated Fourier analysis of the 50M-sampled raw data without average. (a) $S_x\left(\Omega \right)$ for $⟨\left[\Delta \right({\widehat{x}}_{\mathrm{A}}^f-{\widehat{x}}_{\mathrm{B}}^f){]}^2⟩$. (b) $S_p\left(\Omega \right)$ for $⟨\left[\Delta \right({\widehat{p}}_{\mathrm{A}}^f+{\widehat{p}}_{\mathrm{B}}^f){]}^2⟩$. Each trace is normalized to the corresponding vacuum level.

Figure 3

Typical measured correlations. Only 50 points are picked up. (a) and (b) are measured quadrature values within the time interval $T=0.2\mathrm{\mu }\mathrm{s}$ for $x$ and $p$ quadratures, respectively. In each figure, trace (i) is for Alice, while (ii) is for Bob.

Figure 4

Measured correlation diagrams of $10000$ measured values for (a) $x$ and (b) $p$ quadratures.