Experimental subdiffraction source discrimination enabled by spatial demultiplexing and single-photon detectors
Abstract
We experimentally demonstrate a universal, parameter-independent test for asymmetric source discrimination below the diffraction limit. The test exploits spatial-mode demultiplexing (SPADE) and single-photon detection to discriminate the presence of a faint source in the vicinity of a brighter one. We develop a complete theory of the test in the presence of arbitrary modal crosstalk and show that the crosstalk-affected test retains a favorable error exponent over diffraction-limited direct imaging, provided that the crosstalk remains below a threshold Cmax≃ 1/9. This establishes a quantitative condition under which the subdiffraction advantage of SPADE survives realistic imperfections. We experimentally test the scheme for a range of source separations and intensity ratios, without requiring prior knowledge of these parameters. The measured false-negative error rates are in good agreement with the theoretical model and systematically outperform direct imaging. These results demonstrate that SPADE provides a robust and experimentally accessible advantage for asymmetric subdiffraction hypothesis testing in the photon-starved regime, even in the presence of realistic modal crosstalk.
Versions
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BibTeX
@misc{amato2026experimental,
title = {{Experimental subdiffraction source discrimination enabled by spatial demultiplexing and single-photon detectors}},
author = {Luigi Santamaria Amato and Danilo Triggiani and Cosmo Lupo},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2605.15929},
eprint = {2605.15929},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.15929},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Experimental subdiffraction source discrimination enabled by spatial demultiplexing and single-photon detectors
AU - Luigi Santamaria Amato
AU - Danilo Triggiani
AU - Cosmo Lupo
PY - 2026
DA - 2026/10/21
PB - arXiv
DO - 10.48550/arxiv.2605.15929
UR - https://arxiv.org/abs/2605.15929
AB - We experimentally demonstrate a universal, parameter-independent test for asymmetric source discrimination below the diffraction limit. The test exploits spatial-mode demultiplexing (SPADE) and single-photon detection to discriminate the presence of a faint source in the vicinity of a brighter one. We develop a complete theory of the test in the presence of arbitrary modal crosstalk and show that the crosstalk-affected test retains a favorable error exponent over diffraction-limited direct imaging, provided that the crosstalk remains below a threshold C_max≃ 1/9. This establishes a quantitative condition under which the subdiffraction advantage of SPADE survives realistic imperfections. We experimentally test the scheme for a range of source separations and intensity ratios, without requiring prior knowledge of these parameters. The measured false-negative error rates are in good agreement with the theoretical model and systematically outperform direct imaging. These results demonstrate that SPADE provides a robust and experimentally accessible advantage for asymmetric subdiffraction hypothesis testing in the photon-starved regime, even in the presence of realistic modal crosstalk.
ER -