Scientific Results

Quantum-to-classical transition via fuzzy measurements on high-gain spontaneous parametric down-conversion

Year: 2010

Authors: Vitelli C., Spagnolo N., Toffoli L., Sciarrino F., De Martini F.

Autors Affiliation: Dipartimento di Fisica, “Sapienza” Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy; Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Piazzale Aldo Moro 5, I-00185 Roma, Italy; Istituto Nazionale di Ottica Applicata, Largo Fermi 6, I-50125 Firenze, Italy; Accademia Nazionale dei Lincei, via della Lungara 10, I-00165 Roma, Italy

Abstract: We consider the high-gain spontaneous parametric down-conversion in a noncollinear geometry as a paradigmatic scenario to investigate the quantum-to-classical transition by increasing the pump power, that is, the average number of generated photons. The possibility of observing quantum correlations in such a macroscopic quantum system through dichotomic measurement will be analyzed by addressing two different measurement schemes, based on different dichotomization processes. More specifically, we will investigate the persistence of nonlocality in an increasing size n/2-spin singlet state by studying the change in the correlations form as n increases, both in the ideal case and in presence of losses. We observe a fast decrease in the amount of Bell\’s inequality violation for increasing system size. This theoretical analysis is supported by the experimental observation of macro-macro correlations with an average number of photons of about 10(3). Our results shed light on the practical extreme difficulty of observing nonlocality by performing such a dichotomic fuzzy measurement.


Volume: 81 (3)      Pages from: 032123  to: 032123

KeyWords: quantum mechanics; measurement theory; optical tests of quantum theory
DOI: 10.1103/PhysRevA.81.032123

Citations: 26
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