Photon Number Statistics of Multimode Parametric Down-Conversion

We experimentally analyze the complete photon number statistics of parametric down-conversion and ascertain the influence of multimode effects. Our results clearly reveal a difference between single-mode theoretical description and the measured distributions. Further investigations assure the applicability of loss-tolerant photon number reconstruction and prove strict photon number correlation between signal and idler modes.

Figure 1

Scheme of experimental setup (see text); measurement configurations $A$, $B$, $C$, and $D$ provide information about detector efficiency, marginal and collective statistics, and joint correlations, respectively.

Figure 2

(a) Marginal photon number statistics in idler mode for various pump powers; Inset: first probability moments $⟨n^m⟩$ with a fit to a Poissonian distribution. (b) Comparison of signal and idler marginals for lowest and highest pump power; Inset: conditioned statistics demonstrate vacuum suppression. (c) Collective photon pair statistics (see text) for lowest and highest pump powers.

Figure 3

(a) Joint photon statistics $p_{n,m}$ measured with two TMDs and pump power of 220 nW. (b) Marginal statistics of idler with pump power of 375 nW. The measurement is fitted against thermal and Poissonian distributions.