Imaging walk-off–driven distortions in EPR photon-pair correlations
Year: 2026
Type: article
Abstract: Spontaneous parametric down-conversion is the primary source of position-correlated and momentum–anti-correlated photon pairs that form the canonical Einstein–Podolsky–Rosen (EPR) state. Their transverse spatial correlations are usually analyzed within the thin-crystal approximation, where the two-photon wavefunction is assumed to factorize into independent functions of the sum and difference coordinates. In practice, however, birefringence-induced transverse walk-off breaks this factorization and couples these degrees of freedom. Here, we show that this coupling persists even for nominally thin crystals once the free-space propagation of the joint spatial intensity is taken into account. This sum-difference coordinate coupling leads to a distinctive tapering of the transverse correlations near the crystal image plane – an effect that standard factorized models cannot capture. Numerical simulations and experimental data clearly confirm this novel behavior. Our findings provide a more complete description of photon-pair generation in birefringent nonlinear media and clarify fundamental limits on spatially resolved quantum imaging and spatial-mode quantum information processing with EPR states.
Source: Optics Express
DOI: 10.1364/oe.589378
Authors: Christian Howard, Roohollah Ghobadi, Nazanin Dehghan, Alessio D’Errico, Ebrahim Karimi
Language: English
Subfield: Artificial Intelligence
Field: Computer Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,270
Funder: Canada Research Chairs
OpenAlex ID: W4417448505
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