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Description
We generated two-mode entangled states by superposing two squeezed vacuum states from degenerate OPOs via a 50:50 beam splitter (90° phase shift), achieving ∆2(p1 - p2) = -6.14 dB and ∆2(x1 - x2) = -6.17 dB. From the measured covariance matrix, both PPT and EPR criteria were evaluated.However, these only allows us to witness the entanglement, but not to determine the deleterious effects of experimental imperfections due to the beam splitter mixing and the associated mode-mismatch and detection imperfections.We therefore introduce an alternative framework suitable for continuous variable systems using the states’ quantumness, Ξ. This allows us to benchmark the experiment’s performance by comparing the states’ quantumness Ξ′ after the beam splitter mixing with Ξ before. That is a feature unachievable by any standard entanglement criteria.