1201.5289 (Stefan Ast et al.)

Continuous-wave non-classical light with GHz squeezing bandwidth    [PDF]

Stefan Ast, Aiko Samblowski, Moritz Mehmet, Sebastian Steinlechner, Tobias Eberle, Roman Schnabel

Squeezed states can be employed for entanglement-based continuous-variable
quantum key distribution, where the secure key rate is proportional to the
bandwidth of the squeezing. We produced a non-classical continuous-wave laser
field at the telecommunication wavelength of 1550 nm, which showed squeezing
over a bandwidth of more than 2 GHz. The experimental setup used parametric
down-conversion via a periodically poled potassium titanyl phosphate crystal
(PPKTP). We did not use any resonant enhancement for the funda- mental
wavelength, which should in principle allow a production of squeezed light over
the full phase-matching bandwidth of several nanometers. We measured the
squeezing to be up to 0.3 dB below the vacuum noise from 50 MHz to 2 GHz
limited by the measuring bandwidth of the homodyne detector. The squeezing
strength was possibly limited by thermal lensing inside the non-linear crystal.

View original: http://arxiv.org/abs/1201.5289