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arXiv:2201.06249 · Physical Review A

Detecting entanglement between modes of light

Madhura Ghosh Dastidar, Gniewomir Sarbicki

Published Jun 30, 2022• 3 citations
arXivHTMLPDF

Abstract

We consider a subgroup of unitary transformations on a mode of light induced by a Mach-Zehnder Interferometer and an algebra of observables describing a photon-number detector preceded by the interferometer. We explore the uncertainty principles between such observables and their usefulness in performing a Bell-like experiment to show the violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality under the physical assumption that the detector distinguishes between only zero photons and a nonzero number of photons. We show the local settings of the interferometer which lead to a maximal violation of the CHSH inequality.

DOI
10.1103/physreva.105.062459

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We consider a subgroup of unitary transformations on a mode of light induced by a Mach-Zehnder Interferometer and an algebra of observables describing a photon-number detector preceded by the interferometer. We explore the uncertainty principles between such observables and their usefulness in performing a Bell-like experiment to show the violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality under the physical assumption that the detector distinguishes between only zero photons and a nonzero number of photons. We show the local settings of the interferometer which lead to a maximal violation of the CHSH inequality.
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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.
Abstract The Clauser–Horne–Shimony–Holt (CHSH) inequality test is widely used as a mean of invalidating the local deterministic theories. Most attempts to experimentally test nonlocality have presumed unphysical idealizations that do not hold in real experiments, namely, noiseless measurements. We demonstrate an experimental violation of the CHSH inequality that is free of idealization and rules out local models with high confidence. We show that the CHSH inequality can always be violated for any nonzero noise parameter of the measurement. Intriguingly, less entanglement exhibits more nonlocality in the CHSH test with noisy measurements. Furthermore, we theoretically propose and experimentally demonstrate how the CHSH test with noisy measurements can be used to detect weak entanglement on two-qubit states. Our results offer a deeper insight into the relation between entanglement and nonlocality.
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