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Physical Review A

Continuous-variable Bell nonlocality with biphotons produced by spontaneous parametric down-conversion

Jonas B. Araujo, I. G. da Paz, H. A. S. Costa, Carlos H. S. Vieira, Marcos Sampaio

Published Apr 1, 2020• 4 citations
Publisher

Abstract

We revisit a continuous-variable version of the Clauser-Horne-Shimony-Holt inequality with sign binning, first proposed by Bell [J. S. Bell, Speakable and Unspeakable in Quantum Mechanics, 1st ed. (Cambridge University, New York, 1987); Ann. N.Y. Acad. Sci. 480, 263 (1986)]. To explore Bell nonlocality, we use a biphoton effective wave function resulting from a type-I spontaneous parametric down-conversion process. After reviewing the approximations involved in the production and time evolution of such biphotons, we judiciously choose a series expansion for the sinc function part of the biphoton wave function in order to integrate the Wigner function. We conclude that we can qualitatively achieve Bell nonlocality within a regime in which the twin photons are described.

DOI
10.1103/physreva.101.042103

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Entanglement, describing the inseparability of a quantum multiparty system, is one of the most intriguing features of quantum mechanics. Violation of Bell inequality, for ruling out the possibility of local hidden variable theories, is commonly used as a strong witness for quantum entanglement. In previous Bell test experiments with photonic entanglement based on two-photon coincidence measurement, the photon temporal wave packets are absorbed completely by the detectors. That is, the photon coherence time is much shorter than the detection time window. Here we demonstrate generation of frequency-bin entangled narrowband biphotons, and for the first time, test the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality |S|<= 2 for their nonlocal temporal correlations with time-resolved detection. We obtain a maximum |S| value of 2.52+/-0.48 that violates the CHSH inequality. Our result will have applications in quantum information processing involving time-frequency entanglement.
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