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Frontiers in Optics

Spatial Profile and Polarization Entanglement in Partially Spatially Coherent Qubits

Preeti Sharma, Sakshi Rao, Bhaskar Kanseri

Published Jan 1, 2022• 1 citation
Publisher

Abstract

The experimentally observed spatial profile of partially spatially coherent polarization entangled qubit is reported, with the theoretical study for visibility in polarization entanglement test. This study would benefit free-space quantum communications and imaging.
DOI
10.1364/fio.2022.jtu4a.40

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Partially coherent photonic qubits, owing to their robustness in propagation through random media compared to fully coherent qubits, find applications in free-space communication, quantum imaging, and quantum sensing. However, the reduction of spatial coherence degrades entanglement in qubits, adversely affecting entanglement-based applications. We report the recovery of entanglement in the partially coherent photonic qubits generated using a spontaneous parametric downconversion process despite retaining their multimode nature. This study utilizes an electron multiplying charge-coupled device (EMCCD) to perform coincidence measurements, eliminating the need for raster scanning of single-pixel detectors, which simplifies optical alignment, enhances precision, and reduces time consumption. We demonstrate that the size of apertures used to select biphotons substantially impacts the visibility and S-parameter of polarization-entangled partially coherent qubits. The entanglement is recovered with partial spatial coherence properties by choosing small sizes of the apertures in the captured image plane. This study could help in the advancement of free-space quantum communication, quantum imaging, and quantum metrology.
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