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Quantum optics

Quantum entanglement measures Earth’s rotation

Nature Photonics volume 18, page 776 (2024)Cite this article

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Interferometry is one of the most sensitive techniques available to test physical theories and make measurements. In particular, optical ring interferometers based on the Sagnac effect are commonly used to measure rotation, but their performance is constrained by the shot-noise limit. Employing quantum states of light allows for more sensitive optical phase measurements as compared to classical-light scenarios.

Key to their success is the use of a two-photon quantum N00N state, featuring two photons in a superposition of states, where both photons are in one state. These states are known to possess particularly high phase sensitivity, making them valuable for precise measurements in quantum interferometry. In this case, the states are created from the product state of horizontally and vertically polarized photon pairs centred at 1,546 nm and generated by spontaneous parametric down-conversion in a nonlinear optical crystal of poled KTiOPO4.

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  1. Nature Photonics https://www.nature.com/nphoton/

    Giampaolo Pitruzzello

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  1. Giampaolo Pitruzzello
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Correspondence to Giampaolo Pitruzzello.

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Pitruzzello, G. Quantum entanglement measures Earth’s rotation. Nat. Photon. 18, 776 (2024). https://doi.org/10.1038/s41566-024-01490-3

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