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Quantum Physics, quant-ph
Abstract:
Einstein-Podolsky-Rosen (EPR) entanglement is a criterion that is more
demanding than just certifying entanglement. We theoretically and
experimentally analyze the low resource generation of bi-partite continuous
variable entanglement, as realized by mixing a squeezed mode with a vacuum mode
at a balanced beam splitter, i.e. the generation of so-called vacuum-class
entanglement. We find that in order to observe EPR entanglement the total
optical loss must be smaller than 33.3 %. However, arbitrary strong EPR
entanglement is generally possible with this scheme. We realize continuous wave
squeezed light at 1550 nm with up to 9.9 dB of non-classical noise reduction,
which is the highest value at a telecom wavelength so far. Using two phase
controlled balanced homodyne detectors we observe an EPR co-variance product of
0.502 \pm 0.006 < 1, where 1 is the critical value. We discuss the feasibility
of strong Gaussian entanglement and its application for quantum key
distribution in a short-distance fiber network.
