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arXiv · 2605.17974

Measuring the complete set of spatial Schmidt modes of entangled two-photon fields

Radhika Prasad·Nilakshi Senapati·Abhinandan Bhattacharjee·Suman Karan·Anand K. Jha
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Abstract

Spontaneous parametric down-conversion (SPDC) is the most widely-used source of high-dimensional entangled two-photon states, and the entanglement in the spatial degree of freedom is considered best suited for harnessing high-dimensional advantages. Although the Schmidt basis provides a natural choice for state characterisation of entangled two-photon states in any degree of freedom, there is currently no technique that can measure the Schmidt basis of an entangled two-photon field. The existing techniques can only reconstruct the Schmidt spectrum when the Schmidt basis is known a priori. In contrast, we present a technique that measures the complete set of spatial Schmidt modes without any prior knowledge. Using this technique, we report measurement of states with over 3000 Schmidt modes -- highest reported yet -- with up to 98$\%$ fidelity. We expect our work to significantly advance the harnessing of high-dimensional advantages in SPDC-based systems.

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Radhika Prasad, Nilakshi Senapati, Abhinandan Bhattacharjee, Suman Karan, Anand K. Jha. 2026-05-18. Measuring the complete set of spatial Schmidt modes of entangled two-photon fields. https://arxiv.org/abs/2605.17974

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