Entanglement and noise in the above-threshold optical parametric oscillator
P. Nussenzveig, K. N. Cassemiro, Alessandro S. Villar, Paulo Valente, Marcelo Martinelli · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2007
We review the measurement of entanglement in the above-threshold optical parametric oscillator, an experimental challenge that lasted 17 years. The challenge was in part technical, owing to the difficulty of measuring phase noise, but also related to unexpected noise features that remain unexplained. We describe the experimental strategies used to measure phase noise and to circumvent the "extra" noise. The theoretical prediction of a higher order of entanglement is presented, as well as measurements of bright three-color quantum correlations.