Journal
RESULTS IN PHYSICS
Volume 27, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.rinp.2021.104506
Keywords
Partial coherence; Polarization entanglement; Bell test; Concurrence
Funding
- Department of Science and Technology (DST), India under QUEST scheme (DST/ICPS/QUEST/Theme-I/2019)
- Council of Scientific & Industrial Research (CSIR), India
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The study reveals a significant impact of the spatial coherence of the pump on polarization entanglement, and utilizing quantum states for free-space quantum secure communication can offer increased robustness.
We theoretically study the polarization entanglement and the non-local correlations manifested by biphotons using measures as concurrence and CHSH Bell test, generated in the spontaneous parametric down-conversion (SPDC) process for partially spatially coherent pump, affected by the spatial walk-off effects of the extraordinary beam. The study has been carried out for a well-known scheme for generating polarization entanglement utilizing non-collinear, frequency degenerate SPDC process in paired type-I uniaxial crystals. It is found that the polarization entanglement changes drastically with variation in spatial coherence of the pump, offering a possibility to realize a tunable source of polarization entanglement. The study reveals the overriding role of aperture size in compensation of the effect of spatial coherence of pump on the polarization entanglement and non-local correlations, especially in the conservation of polarization entanglement for incoherent and partially coherent pump beams. Free-space quantum secure communication utilizing these quantum states possessing maximal entanglement and partially spatially coherent properties would essentially offer robustness to the losses on propagation through atmospheric turbulence, resulting in a significant enhancement in the key rate.
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