Sub-shot-noise photon-number correlation in the parties of a mesoscopic twin-beam

This work demonstrates sub-shot-noise limit (SNL) correlations between the photon numbers detected (~ 1000/pulse) in the two parties of a frequency non-degenerate ps-pulsed twin-beam that is obtained by a type I SPDC interaction in a beta-BaB
₂
O
₄
crystal of 4-mm thickness (Fujian Castech Crystals, China) pumped by the frequency-tripled output ( lambda
_p
= 349 nm) of a cw mode-locked Nd:YLF laser regeneratively amplified at 500 Hz (high Q laser production, Austria).