Study of spdc wavefunction propagation and its unique properties

Mandal, Saptak (2025) Study of spdc wavefunction propagation and its unique properties. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Saptak Mandal (20MS016)) 20MS016_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (5MB)

Abstract

The transverse spatial entanglement of biphotons generated through spontaneous parametric down-conversion (SPDC) is a significant promoter for both theoretical investigations and practical uses in quantum optics. This resource enables access to a diverse range of quantum states, including the fascinating phase-entangled state, where the entanglement is present only in the complex phase of the wave function rather than in the traditional position or momentum domains. In this state, while standard position or momentum correlations may disappear as they propagate, the overall quantum entanglement remains entirely intact, uncovering new opportunities to explore the subtle characteristics of quantum light. The experimental monitoring approach presented here measures entire propagation distance scales for photon number correlations while reducing the infinite domain system into a measurable range through single-lens imaging. The amplitude correlation disappears precisely at the phase-entanglement plane in accordance with Double Gaussian model theoretical calculations. Phase correlation functions were investigated more closely through direct experimental assessment using double slits during a two-photon interference test. During this experiment the pattern of interference exhibited fundamental differences from common position-correlated setups according to joint probability calculations. The obtained results enhance our understanding of two-photon quantum coherence specifics while providing possibilities to improve quantum imaging methods and metrology and holographic technologies.

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