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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Entanglement and noise in the above-threshold optical parametric oscillator

P. Nussenzveig, K. N. Cassemiro, Alessandro S. Villar, Paulo Valente, M. Martinelli

Published Jun 7, 2007• 0 citations
Publisher

Abstract

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.

DOI
10.1117/12.725466

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We investigate entanglement in the above-threshold optical parametric oscillator, both theoretically and experimentally, and discuss its potential applications to quantum information. The fluctuations measured in the subtraction of signal and idler amplitude quadratures are Δ2p̂−=0.50(1), or −3.01(9) dB, and in the sum of phase quadratures they are Δ2q̂+=0.73(1), or −1.37(6) dB. A detailed experimental study of the noise behavior as a function of pump power is presented, and the discrepancies with theory are discussed.