Investigating the quantum properties of the field in the optical parametric oscillator based on rubidium atoms

Author(s)

Alvaro Montaña Guerrero

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2022-11-30

Examining board members

Marcelo Martinelli; Gabriel Horacio Aguilar; Nestor Felipe Caticha Alfonso; Diogo de Oliveira Soares Pinto; Pablo Lima Saldanha

• Advisor: Marcelo Martinelli

Abstract

In the present thesis, we show the measurement of entanglement in an optical parametric oscillator (OPO) based on the parametric four-wave mixing process (FWM) in 85Rb vapor, above the oscillation threshold. This corresponds to the first measure of entanglement in an OPO with susceptibility 3. The FWM, the base process for the construction of this OPO, takes place in 3 non-linear media, as is the case with the isotope of 85Rb. As a preliminary to the construction of the OPO, we carried out a review of the classical and quantum theory of the FWM, as well as the experimental obtained of the FWM process around the D1 line of absorption of the 85Rb. The high gain of the FWM process and the use of open cavities allows the design and the construction of a doubly resonant OPO, which generates two beams known as signal and complementary. We show the first squeezing measurement between the signal and complementary beams generated by our OPO, with a maximum squeezing level at the intensity difference of -2.7 dB [1]. Squeezing is robust for high pump beam powers, which allows stable operation of the OPO at values up to four times the threshold. In addition, we reconstruct the covariance matrix associated with the state of the two beams. The covariance matrix allows performing the entanglement test, using the criteria of Duan et. al. [2] and Simon [3]. We show, for the first time, entanglement between the two beams generated by the OPO [4], demonstrating the violation of Duan\'s criterion, with a maximum value of 2 p-+2 q+=1.56 (14). By using Simon\'s criterion, we were able to study the entanglement between the different sidebands of the system, with a higher entanglement level for specific bipartition pairs. We show that atomic density is a determining factor for the generation and loss of quantum correlations. The generation of entangled beams with an atomic OPO working close to the resonance of alkali atoms, allows for natural integration into quantum networks. (AU)

• FAPESP's process: 17/27216-4 - Studying the quantum state of the field at the threshold of the optical parametric oscillator
• Grantee: Alvaro Montaña Guerrero
• Support Opportunities: Scholarships in Brazil - Doctorate