Indistinguishable MHz-narrow heralded photon pairs from a whispering gallery resonator

Huang SH, Dirmeier T, Shafiee G, Laiho K, Strekalov DV, Aiello A, Leuchs G, Marquardt C (2025)

Publication Type: Journal article

Publication year: 2025

Journal

Book Volume: 10

Article Number: 056111

Journal Issue: 5

DOI: 10.1063/5.0263312

Abstract

The Hong-Ou-Mandel interference plays a vital role in many quantum optical applications where indistinguishability of two photons is important. Such photon pairs are commonly generated as the signal and idler in the polarization-degenerate spontaneous parametric downconversion (SPDC). To scale this approach to a larger number of photons, we demonstrate how two independent signal photons radiated into different spatial modes can be rendered conditionally indistinguishable by a heralding measurement performed on their respective idlers. We use the SPDC in a whispering gallery resonator, which is already proven to be versatile sources of quantum states. Its extreme conversion efficiency allowed us to perform our measurements with only 50 nW of in-coupled pump power in each propagation direction. The Hong-Ou-Mandel interference of two counterpropagating signal photons manifested itself in the fourfold coincidence rate, where the detection of two idler photons heralds a pair of signal photons with a desired temporal overlap. We achieved the Hong-Ou-Mandel dip contrast of 74% ± 5%. Importantly, the optical bandwidth of all involved photons is of the order of a MHz and is continuously tunable. This, on the one hand, makes it possible to achieve the necessary temporal measurement resolution with standard electronics and, on the other hand, creates a quantum state source compatible with other candidates for qubit implementation, such as optical transitions in solid-state or vaporous systems. We also discuss the possibility of generating photon pairs with similar temporal modes from two different whispering gallery resonators.

Authors with CRIS profile

Involved external institutions

Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR) / German Aerospace Center Germany (DE) Max-Planck-Institut für die Physik des Lichts (MPL) / Max Planck Institute for the Science of Light Germany (DE)

How to cite

APA:

Huang, S.-H., Dirmeier, T., Shafiee, G., Laiho, K., Strekalov, D.V., Aiello, A.,... Marquardt, C. (2025). Indistinguishable MHz-narrow heralded photon pairs from a whispering gallery resonator. APL Photonics, 10(5). https://doi.org/10.1063/5.0263312

MLA:

Huang, Sheng-Hsuan, et al. "Indistinguishable MHz-narrow heralded photon pairs from a whispering gallery resonator." APL Photonics 10.5 (2025).

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