Multicolor entanglement for quantum information network.

Author(s)

Antonio Sales Oliveira Coelho

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2013-04-19

Examining board members

Paulo Alberto Nussenzveig; Daniel Felinto Pires Barbosa; Alexandre Levine; Gustavo Garcia Rigolin; Marcelo Paleologo Elefteriadis de França Santos

• Advisor: Paulo Alberto Nussenzveig

Abstract

We present in this thesis the first direct generation of tripartite entanglement among bright beams of light. We measured the entanglement among signal, idler and reflected pump beams, produced by an Optical Parametric Oscillator (OPO) operating above the threshold. The main feature of our system is the difference between the wavelengths of the fields (l0 = 532.251 nm, l1 = 1062.102 nm, e l2 = 1066.915 nm). This is the first measurement of entanglement among more than two subsystems produced by a single source, in a continuous variable system. In order to investigate the existence of entanglement, we applied the criterion of positivity under partial transposition (PPT). This criterion, applied to systems composed of Gaussian states, arranged in 1×(N1) bipartition, becomes necessary and sufficient to demonstrate entanglement. We also characterized the entanglement when the fields are submitted to losses, identifying regions of parameters where the states have fragile or robust entanglement. To ensure that we are dealing with Gaussian states, we investigate the statistics of the fields, showing excelent agreement among values of higher order moments of the photocurrent measured and expected values for a Gaussian distribution. The present study is an important step in the development of a quantum information network formed by different physical systems. (AU)

• FAPESP's process: 08/58297-0 - Multicolor entanglement for quantum information networks
• Grantee: Antônio Sales Oliveira Coelho
• Support Opportunities: Scholarships in Brazil - Doctorate