13 dB squeezed vacuum states at 1550 nm from 12 mW external pump power at 775 nm.

Abstract

Strongly squeezed light at telecommunication wavelengths is a necessary resource for one-sided device-independent quantum key distribution via fiber networks. Reducing the optical pump power that is required for its generation will advance this quantum technology towards efficient out-of-laboratory operation. Here, we investigate the second-harmonic pump power requirement for parametric generation of continuous-wave squeezed vacuum states at 1550nm in a state-of-the-art doubly resonant standing-wave periodically poled potassium titanyl phosphate cavity setup. We use coarse adjustment of the Gouy phase via the cavity length, together with temperature fine-tuning, for simultaneously achieving double resonance and (quasi) phase matching, and observe a squeeze factor of 13dB at 1550nm from just 12mW of external pump power at 775nm. We anticipate that optimizing the cavity coupler reflectivity will reduce the external pump power to 3mW, without reducing the squeeze factor.