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Quantum Information and Measurement (QIM)

Photon Entanglement In Strongly Non-Degenerate Parametric Down Conversion And Its Applications

Roman V. Zakharov, Olga V. Tikhonova

Published Jan 1, 2019• 0 citations
Publisher
DOI
10.1364/qim.2019.f5a.2

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Abstract Parametric down conversion in a strongly non-degenerate regime with output terahertz (THz) and optical beams is investigated. The theoretical approach based on the concept of independent Schmidt modes is developed and the shapes and weights of optical and THz Schmidt modes are analyzed both in a far-field and near-field regions. Analytical approximation for examined radial Schmidt modes is found. Strong azimuthal correlations between optical and THz photons are established. THz photons are shown to be involved simultaneously both in parametric down conversion and sum frequency generation processes. Photons in THz, Stocks and anti-Stocks channels are demonstrated to be strongly entangled. Methods to examine the properties of the THz radiation by measuring the correlations between generated Stocks and anti-Stocks components are suggested.

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Abstract Parametric down conversion in a strongly non-degenerate regime with output terahertz (THz) and optical beams is investigated. The theoretical approach based on the concept of independent Schmidt modes is developed and the shapes and weights of optical and THz Schmidt modes are analyzed both in a far-field and near-field regions. Analytical approximation for examined radial Schmidt modes is found. Strong azimuthal correlations between optical and THz photons are established. THz photons are shown to be involved simultaneously both in parametric down conversion and sum frequency generation processes. Photons in THz, Stocks and anti-Stocks channels are demonstrated to be strongly entangled. Methods to examine the properties of the THz radiation by measuring the correlations between generated Stocks and anti-Stocks components are suggested.
We demonstrate the novel effect of gain-induced spectral shifts in the type-II parametric down-conversion (PDC) process, which results in a transition from degenerate to non-degenerate PDC with increasing parametric gain. This effect, originating from the second-order dispersion terms, significantly alters the properties of PDC in the high-gain regime, where it leads to increased distinguishability of the generated photon pairs. The effect is established by evaluating a rigorous theoretical model, which is based on solving a system of coupled integro-differential equations for monochromatic operators. The widely used spatially-averaged approximate model fails to reproduce this important effect.