Hyperentanglement in intermediate phase-space planes: benchmarking a photon-pair source for quantum key distribution
Abstract
We characterize a source of photon pairs simultaneously entangled in polarization and in the transverse spatial degree of freedom, with the spatial measurements performed in intermediate planes of the fractional Fourier transform. The source consists of two crossed type-I crystals in a non-collinear geometry, such that the transverse variables carry information about the crystal of origin. Detection in the crystal plane reveals this information completely and destroys the polarization entanglement, so that a scheme using the near and far fields as conjugate spatial bases cannot support a parallel polarization channel. In intermediate planes both spatial bases combine position and momentum, such that the which-crystal information is partially erased, and the polarization entanglement survives in all four combinations of spatial bases. Applying Bell and Einstein-Podolsky-Rosen criteria to the same photon pairs certifies both degrees of freedom simultaneously. We evaluate quantum bit error rates and asymptotic secret key rates in each degree of freedom, and find that the source delivers two simultaneously usable channels per photon pair.
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BibTeX
@misc{magiotto2026hyperentanglement,
title = {{Hyperentanglement in intermediate phase-space planes: benchmarking a photon-pair source for quantum key distribution}},
author = {Murilo H. Magiotto and Millena B. Novaes and Wesley B. Cardoso and Ardiley T. Avelar and 1 Paulo H. Souto Ribeiro and Stephen P. Walborn and Guilherme L. Zanin and Rafael M. Gomes},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.20005},
eprint = {2610.20005},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.20005},
}
RIS
TY - UNPB
TI - Hyperentanglement in intermediate phase-space planes: benchmarking a photon-pair source for quantum key distribution
AU - Murilo H. Magiotto
AU - Millena B. Novaes
AU - Wesley B. Cardoso
AU - Ardiley T. Avelar
AU - 1 Paulo H. Souto Ribeiro
AU - Stephen P. Walborn
AU - Guilherme L. Zanin
AU - Rafael M. Gomes
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2610.20005
UR - https://arxiv.org/abs/2610.20005
AB - We characterize a source of photon pairs simultaneously entangled in polarization and in the transverse spatial degree of freedom, with the spatial measurements performed in intermediate planes of the fractional Fourier transform. The source consists of two crossed type-I crystals in a non-collinear geometry, such that the transverse variables carry information about the crystal of origin. Detection in the crystal plane reveals this information completely and destroys the polarization entanglement, so that a scheme using the near and far fields as conjugate spatial bases cannot support a parallel polarization channel. In intermediate planes both spatial bases combine position and momentum, such that the which-crystal information is partially erased, and the polarization entanglement survives in all four combinations of spatial bases. Applying Bell and Einstein-Podolsky-Rosen criteria to the same photon pairs certifies both degrees of freedom simultaneously. We evaluate quantum bit error rates and asymptotic secret key rates in each degree of freedom, and find that the source delivers two simultaneously usable channels per photon pair.
ER -