We investigate the quantum properties of the light beams produced by an optical parametric oscillator (OPO) above threshold, both experimentally and theoretically. We present the first measurement of entanglement between the bright twin beams, signal and idler. These may differ in wavelength by hundreds of nanometers, showing different 'colors'. This special characteristic allows for the transfer of quantum information between different regions of the electromagnetic spectrum. Entanglement was experimentally demonstrated by showing that the sum of variances of two EPR-like observables, the subtraction of the beams intensities and the sum of their phases, violates an inequality necessarily fulfilled by all separable states. We obtained squeezing in both observables, with the respective values ∆ 2p − = 0,49(1) and ∆ 2q + = 0,65(1) relative to the shot noise level. The violated inequality resulted ∆ 2p − + ∆ 2q + = 1,14(2)< 2. This solved an old problem, enunciated in 1988, when this effect was theoretically predicted for the first time. We show theoretically that the quantum correlations extend to the pump beam reflected by the OPO as well, culminating in entanglement among the three fields involved in the parametric process. Therefore, the OPO actually produces tripartite entanglement among very distant spectral regions in a direct manner. Multicolor entanglement opens new possibilities in the frequency conversion of quantum information. The improvements we performed in our system in order to achieve this result have brought a deeper understanding of the phenomena involved, as well as a more stable system operation, resulting in the development of a reliable source of bright entangled light beams. This work has finally added the above-threshold OPO to the optical quantum information toolbox. We expect new and exciting applications to come in the near future. Agradecimentos A Ciênciaé das mais nobres atividades humanas e, como tal, faz uso de alguns de nossos melhores traços: a curiosidade, o livre-pensamento, o diletantismo e a busca pela verdade. Sanar nossa ignorância acerca dos fatos materiaisà volta pode facilitar-nos a descoberta daquilo que realmente importa. Por isso, o pensamento científicoé para a razão o que representa a arte para a emoção. E neste mundo de ilusões, governado pelas vontades de genes forjados em milhões de inóspitos anos, a Ciência nos redime como espécie, mostrando-nos que possuímos algum valor, e nos auxilia na hercúlea tarefa de divisar novos 'genes' para o futuro. Agradeço primeiramenteàs grandes mentes que perceberam a necessidade de se construir e manter esta ilha de irrealidade queé o mundo acadêmico, para formar cérebros capazes de responder aos desafios da realidade urgente (embora, em nosso país, ainda haja muitos obstáculos a essa união), e aos bravos que (ainda!) lutam diariamente contra a contaminação deste mundo por outras realidades. Agradeçoàs pessoas desta Instituição que mais do que cumpriram suas tarefas de apoioàs atividades científicas: aos excelentes professores, Bar...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.