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Quantum information with continuous variables of atoms and light


Quantum Information Science attracts considerable attention owing to its fundamental character, on the one hand, since information is physical, meaning that physical systems are needed to store, process, and transmit it; and, on the other hand, to the potential technological applications. Since present-day computing is based on binary logic, it is natural to search for extensions in discrete quantum systems, containing only two levels, the so-called quantum bits, or qubits. There is, nevertheless, a growing interest in the use of continuous variable systems, typically in Quantum Optics, because techniques for creation and detection of non-classical states of light are well-known and mastered. Our group is among the few in Brazil to work on continuous variable systems, especially from the experimental viewpoint. We have studied the interaction of light with coherently prepared atomic media in the framework of Electromagnetically Induced Transparency, EIT. We have also studied entanglement between the bright beams produced by an Optical Parametric Oscillator (OPO). In the next four years, we expect to perform a series of experiments, mainly to: study a quantum key distribution protocol, using the entangled twin beams from the OPO; implement quantum teleportation with color conversion, by using the (frequency) nondegenerate twin beams (this is already funded, in a project awarded to Prof. Marcelo Martinelli; no supplementary funding is requested for this investigation here); study the recently generated pump-signal-idler tripartite entanglement in the OPO; study the phenomenon of "entanglement sudden death" in continuous variable systems, recently discovered by us; use the tripartite entanglement for quantum information tasks, such as communications; observe non-classical properties of light, such as squeezing and entanglement, by interaction with coherently prepared atomic media; investigate, both theoretically and experimentally, ways to exchange quantum information between atomic systems and bright light beams, bringing together these two general research subjects. (AU)

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Scientific publications (10)
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
BARBOSA, F. A. S.; COELHO, A. S.; CASSEMIRO, K. N.; NUSSENZVEIG, P.; FABRE, C.; VILLAR, A. S.; MARTINELLI, M.. Quantum state reconstruction of spectral field modes: Homodyne and resonator detection schemes. Physical Review A, v. 88, n. 5, . (10/08448-2, 09/52157-5, 10/52282-1)
THEOPHILO, K.; KUMAR, A.; FLOREZ, H. M.; GONZALEZ-ARCINIEGAS, C.; NUSSENZVEIG, P.; MARTINELLI, M.. Probing light forces on cold atoms by noise correlation spectroscopy. Physical Review A, v. 98, n. 5, . (10/08448-2)
BARBOSA, F. A. S.; COELHO, A. S.; CASSEMIRO, K. N.; MARTINELLI, M.; NUSSENZVEIG, P.; VILLAR, A. S.. Assumption-free measurement of the quantum state of light: Exploring the sidebands of intense fields. Physical Review A, v. 102, n. 6, . (10/08448-2, 09/52157-5, 10/52282-1, 15/18834-0)
COELHO, A. S.; BARBOSA, F. A. S.; CASSEMIRO, K. N.; MARTINELLI, M.; VILLAR, A. S.; NUSSENZVEIG, P.. Analyzing the Gaussian character of the spectral quantum state of light via quantum noise measurements. Physical Review A, v. 92, n. 1, . (10/08448-2, 10/52282-1)
RODRIGUES, R. B.; GONZALES, J.; PINHEIRO DA SILVA, B.; HUGUENIN, J. A. O.; MARTINELLI, M.; MEDEIROS DE ARAUJO, R.; SOUZA, C. E. R.; KHOURY, A. Z.. Orbital angular momentum symmetry in a driven optical parametric oscillator. OPTICS LETTERS, v. 43, n. 11, p. 2486-2489, . (10/08448-2)
FLOREZ, H. M.; KUMAR, A.; THEOPHILO, K.; NUSSENZVEIG, P.; MARTINELLI, M.. Correlation spectroscopy in cold atoms: Light sideband resonances in electromagnetically-induced-transparency condition. Physical Review A, v. 94, n. 1, . (10/08448-2)
BARBOSA, F. A. S.; COELHO, A. S.; CASSEMIRO, K. N.; NUSSENZVEIG, P.; FABRE, C.; MARTINELLI, M.; VILLAR, A. S.. Beyond Spectral Homodyne Detection: Complete Quantum Measurement of Spectral Modes of Light. Physical Review Letters, v. 111, n. 20, . (10/08448-2, 09/52157-5, 10/52282-1)
FLOREZ, H. M.; CRUZ, L. S.; DE MIRANDA, M. H. G.; DE OLIVEIRA, R. A.; TABOSA, J. W. R.; MARTINELLI, M.; FELINTO, D.. Power-broadening-free correlation spectroscopy in cold atoms. Physical Review A, v. 88, n. 3, . (10/08448-2)
MUNOZ-MARTINEZ, LUIS F.; SILVA BARBOSA, FELIPPE ALEXANDRE; COELHO, ANTONIO SALES; ORTIZ-GUTIERREZ, LUIS; MARTINELLI, MARCELO; NUSSENZVEIG, PAULO; VILLAR, ALESSANDRO S.. Exploring six modes of an optical parametric oscillator. Physical Review A, v. 98, n. 2, . (10/08448-2)
BARBOSA, F. A. S.; COELHO, A. S.; MUNOZ-MARTINEZ, L. F.; ORTIZ-GUTIERREZ, L.; VILLAR, A. S.; NUSSENZVEIG, P.; MARTINELLI, M.. Hexapartite Entanglement in an above-Threshold Optical Parametric Oscillator. Physical Review Letters, v. 121, n. 7, . (10/08448-2)

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