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Quantum 2.0 Conference and Exhibition

Violating Bell’s Inequality with Single-Photon Entangled States using Self-Referential Measurements

Daniel Kun, Teodor Strömberg, Borivoje Dakić, Philip John Walther, Lee A. Rozema

Published Jan 1, 2025• 0 citations
Publisher

Abstract

We violate a CHSH inequality using two copies of single-photon entangled states, simultaneously verifying their entangled nature without the need for post-selection or local oscillators.
DOI
10.1364/quantum.2025.qm3b.6

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The violation of Bell-like inequalities unambiguously verifies the entanglement of a multipartite quantum state. However, experimental impairments and nonidealities often compromise the entanglement quality, and this degradation translates into a nonmaximal violation of these inequalities. We present a detailed analysis of the influence of experimental impairments on the quality of nonlocal polarization entanglement for a two-qubit state as measured by the Clauser–Horne–Shimony–Holt parameter, with a particular emphasis on beamsplitters, polarization controllers, filters, and photon sources. This analysis allows the identification of the impairments that are critical and that need to be specifically monitored at the experimental level.