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arXiv:2602.10317

High-performance source of indistinguishable polarization-entangled photons with a local oscillator reference for quantum networking

Michael Grayson, Shawn Meyer, Daniel Sorensen, Abigail Gookin, Markus Allgaier, Nicholas V. Nardelli, Tara M. Fortier, Dileep V. Reddy, Martin J. Stevens, Michael D. Mazurek, Juliet T. Gopinath, L. Krister Shalm

quant-phphysics.opticsSubmitted Feb 10, 2026• Announced Feb 12, 2026• 2 citations• Revised Apr 14, 2026 (v2)
v1 · Feb 10, 2026v2 · Apr 14, 2026
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Abstract

Optical quantum networking protocols impose stringent requirements on the states produced by sources of entanglement. We demonstrate a free-space, compact, source of indistinguishable pairs of polarization entangled photons, with an integrated local oscillator reference as a significant step towards this goal. This source achieves $(99.11 \pm 0.01) \%$ polarization entanglement visibility, $(96.3 \pm 0.6) \%$ successive-photon Hong-Ou-Mandel interference visibility, $(68.0 \pm 0.1$) \% heralded efficiency as detected, and $(88.6 \pm 0.2) \%$ interference visibility with a local oscillator. This simultaneous achievement of state-of-the-art metrics demonstrates an adaptable platform for quantum networking.

Comments
23 pages, 3 figures, preprint

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Optical quantum networking protocols impose stringent requirements on the states produced by sources of entanglement. We demonstrate a free-space, compact source of indistinguishable pairs of polarization-entangled photons, with an integrated local oscillator reference as a significant step towards this goal. This source achieves (99.11±0.01)% polarization entanglement visibility, (96.3±0.6)% successive-photon Hong–Ou–Mandel interference visibility, (68.0±0.1)% heralded efficiency as detected, and (88.6±0.2)% interference visibility with a local oscillator. This simultaneous achievement of state-of-the-art metrics demonstrates an adaptable platform for quantum networking.
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We present a source of polarization entangled photon pairs based on spontaneous parametric downconversion engineered for frequency uncorrelated telecom photon generation. Our source provides photon pairs that display, simultaneously, the key properties for high-performance quantum information and fundamental quantum science tasks. Specifically, the source provides for high heralding efficiency, high quantum state purity and high entangled state fidelity at the same time. Among different tests we apply to our source we observe almost perfect non-classical interference between photons from independent sources with a visibility of (100 ± 5)%.
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