Experimental characterization of photon-number noise in Rarity-Tapster-Loudon-type interferometers

In this paper, we develop a simple model describing inherent photon-number noise in Rarity-Tapster-Loudon-type interferometers. This noise is caused by generating photon pairs in the process of spontaneous parametric down-conversion and adding a third photon by attenuating the fundamental laser mode to the single-photon level. We experimentally verify our model and present resulting signal-to-noise ratios as well as obtained three-photon generation rates as functions of various setup parameters. Subsequently we evaluate the impact of this particular source of noise on quantum teleportation which is a key quantum information protocol using this interferometric configuration.

Figure 1

Setup of the experiment. (1) Idler mode, (2) signal mode, (3) attenuated fundamental laser mode, [IF(1-3)] interference filters (3 nm in FWHM), [NDF(1,3)] neutral density filter, [S(2,3)] shutters, (SHG) second harmonics generation, (Mira) Ti-sapphire fs laser (central wavelength of 826 nm, FWHM of 11 nm), (BBO) a $\beta -\mathrm{BaB}{}_2\mathrm{O}{}_4$ crystal for SPDC.

Figure 2

Dependence of SNR on parameter $R$. Points visualize experimentally observed results. Lines correspond to various levels of expansion in Eq. (9): to 2 (green dashed line), 3 (black solid line), and 4 (magenta dashed-dot line) terms.

Figure 3

(a) Dependence of SNR on genuine coincidence rate $C{C}_g$. Points visualize experimentally observed results; the solid blue line depicts fitted experimental data with theoretical dependence based on Eq. (16). (b) Dependence of $C{C}_g$ on $P_p$. The dashed green line depicts fitted experimental data with theoretical dependence based on Eq. (10).

Figure 4

Dependence of $C{C}_g$ on attenuation factors (a) $A_1$, solid green line, and (b) $A_2$, dashed orange line. Points visualize experimentally observed results; lines depict fitted experimental data with theoretical fit based on Eq. (17).

Figure 5

Dependence of average fidelity $\langle F\rangle$ on SNR. Points visualize calculated results from experimentally observed SNRs. The solid blue line corresponds to our theoretical model, the dotted red line is the classical protocol limit ($F=2/3$) [35], and the dashed green line indicates the secure teleportation, i.e., $F=5/6$ cloning threshold; see [33].