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Frontiers in Optics

Quantum-Enhanced Interferometry Via Extreme Non-Degenerate Energy-Entangled Photons

Colin P. Lualdi, Kristina A. Meier, Spencer J. Johnson, Paul G. Kwiat

Published Jan 1, 2021• 1 citation
Publisher

Abstract

We perform two-photon interference with highly non-degenerate frequency-entangled photons. Our system improves on existing interferometers by promising attosecond temporal resolution while offering robustness against dispersion, background, and loss.
DOI
10.1364/fio.2021.fth6d.2

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In classical optical interferometry, loss and background complicate achieving fast nanometer-resolution measurements with illumination at low light levels. Conversely, quantum two-photon interference is unaffected by loss and background, but nanometer-scale resolution is physically difficult to realize. As a solution, we enhance two-photon interference with highly nondegenerate energy entanglement featuring photon frequencies separated by 177 THz. We observe measurement resolution at the nanometer (attosecond) scale with only O (10 4 ) photon pairs, despite the presence of background and loss. Our nondestructive thickness measurement of a metallic thin film agrees with atomic force microscopy, which often achieves better resolution via destructive means. With contactless, nondestructive measurements in seconds or faster, our instrument enables metrological studies in optically challenging contexts where background, loss, or photosensitivity are factors.