ausblenden:
Schlagwörter:
Quantum Physics, quant-ph, Physics, Optics, physics.optics
Zusammenfassung:
The distribution of entanglement with Gaussian statistic can be used to
generate a mathematically-proven secure key for quantum cryptography. The
distributed secret key rate is limited by the {entanglement strength, the
entanglement bandwidth and the bandwidth of the photo-electric detectors}. The
development of a source for strongly, bi-partite entangled light with high
bandwidth promises an increased measurement speed and a linear boost in the
secure data rate. Here, we present the experimental realization of a Gaussian
entanglement source with a bandwidth of more than 1.25\,GHz. The entanglement
spectrum was measured with balanced homodyne detectors and was quantified via
the inseparability criterion introduced by Duan and coworkers with a critical
value of 4 below which entanglement is certified. Our measurements yielded an
inseparability value of about 1.8 at a frequency of 300\,MHz to about 2.8 at
1.2\,GHz extending further to about 3.1 at 1.48\,GHz. In the experiment we used
two 2.6\,mm long monolithic periodically poled potassium titanyl phosphate
(PPKTP) resonators to generate two squeezed fields at the telecommunication
wavelength of 1550\,nm. Our result proves the possibility of generating and
detecting strong continuous-variable entanglement with high speed.
