Experimental Observation of Purity-Like Invariants of Multi-photon States in Linear Optics
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arXiv
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| Autores principales: | , , , , , |
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| Formato: | Preprint |
| Publicado: |
2025
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| _version_ | 1866916794955988992 |
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| author | Yang, Baichuan Zhan, Hao Mi, Minghao Zhang, Aonan Xu, Liang Zhang, Lijian |
| author_facet | Yang, Baichuan Zhan, Hao Mi, Minghao Zhang, Aonan Xu, Liang Zhang, Lijian |
| contents | Linear optical networks (LONs) with multi-photon inputs offer a powerful platform for advanced quantum technologies. However, the number of degrees of freedom of a LON is far fewer than the dimensionality of the multi-photon multi-mode Fock space, therefore it cannot implement arbitrary unitary evolutions on multi-photon states. Understanding these intrinsic constraints is essential for the preparation, manipulation, and measurement of multi-photon states with LONs. Although several properties of the multi-photon state have been shown to be invariant under LON unitary evolution, their physical interpretation remains elusive. Here, we introduce a Hermitian transfer matrix approach to explore the multi-photon evolution, revealing that the overall state purity decomposes into three distinct invariants -- each arising from either single-photon dynamics or the multi-photon interference. We experimentally observe these purity-like invariants by preparing distinct initial states, applying LON unitaries, and measuring the resulting invariants. Our results not only confirm their conservation but also provide valuable insights into multi-photon state evolution in linear optics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2506_12857 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Experimental Observation of Purity-Like Invariants of Multi-photon States in Linear Optics Yang, Baichuan Zhan, Hao Mi, Minghao Zhang, Aonan Xu, Liang Zhang, Lijian Quantum Physics Linear optical networks (LONs) with multi-photon inputs offer a powerful platform for advanced quantum technologies. However, the number of degrees of freedom of a LON is far fewer than the dimensionality of the multi-photon multi-mode Fock space, therefore it cannot implement arbitrary unitary evolutions on multi-photon states. Understanding these intrinsic constraints is essential for the preparation, manipulation, and measurement of multi-photon states with LONs. Although several properties of the multi-photon state have been shown to be invariant under LON unitary evolution, their physical interpretation remains elusive. Here, we introduce a Hermitian transfer matrix approach to explore the multi-photon evolution, revealing that the overall state purity decomposes into three distinct invariants -- each arising from either single-photon dynamics or the multi-photon interference. We experimentally observe these purity-like invariants by preparing distinct initial states, applying LON unitaries, and measuring the resulting invariants. Our results not only confirm their conservation but also provide valuable insights into multi-photon state evolution in linear optics. |
| title | Experimental Observation of Purity-Like Invariants of Multi-photon States in Linear Optics |
| topic | Quantum Physics |
| url | https://arxiv.org/abs/2506.12857 |