Stuttgart 2012 – wissenschaftliches Programm
Q 35.79: Poster
Mittwoch, 14. März 2012, 16:30–19:00, Poster.I+II
Continuous-wave light with a GHz squeezing bandwidth — •Stefan Ast, Aiko Samblowski, Moritz Mehmet, Sebastian Steinlechner, Tobias Eberle, Henning Vahlbruch, and Roman Schnabel — Institut für Gravitationsphysik, Hannover
Two-mode squeezed states can be used for entanglement-based continuous-variable quantum key distribution. The secure key rate is proportional to the bandwidth of the squeezing. We produced a continuous-wave squeezed state at the telecommunication wavelength of 1550 nm with a squeezing bandwidth of more than 2 GHz. The experimental setup used optical parametric down conversion (PDC) via a periodically poled potassium titanyl phosphate crystal (PPKTP) inside an optical cavity. To enhance the intra-cavity pump for the PDC process the resonator had a high Finesse for the harmonic wavelength at 775 nm. For the fundamental wavelength of 1550 nm there was no resonant enhancement, which should allow to produce the squeezed light within the phase-matching bandwidth of 3.22 nm. The squeezing was measured to be up to 0.3 dB below the vacuum noise from 50-2000 MHz. The squeezing strength was possibly limited by high thermal effects inside the non-linear crystal due to a high intra cavity pump power.