Towards Schr\"odinger Cat States in the Second Harmonic Generation

Quantum Physics [Submitted on 25 Mar 2026] Towards Schrödinger Cat States in the Second Harmonic Generation Ranjit Singh, Leonid A. Barinov, Grigori G. Amosov, Anatoly V. Masalov We investigate the quantum evolution of the pump field in second-harmonic generation under strong pump depletion. Starting from a coherent state, the pump develops a nonclassical phase-space structure resembling a Schrödinger cat state. This behavior originates from phase instability induced by vacuum fluctuations of the harmonic mode. A rigorous quantum analysis has been performed for mean photon numbers up to \langle \hat n \rangle = 100 in pump mode. For larger photon numbers, up to \langle \hat n \rangle = 10^{7}, the dynamics have been analyzed using a classical trajectory method with sampled initial conditions that reproduces the main features of the quantum evolution. The results indicate that nonlinear frequency conversion can generate macroscopic superposition-like states of the pump field. Although the resulting state is not pure due to correlations with the second-harmonic wave, it remains non-classical with negative zones of Wigner function. These results indicate that strongly nonlinear frequency conversion can provide a scalable route toward macroscopic nonclassical states of light. Subjects: Quantum Physics (quant-ph); Optics (physics.optics) Cite as: arXiv:2603.24067 [quant-ph]   (or arXiv:2603.24067v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2603.24067 Focus to learn more Submission history From: Ranjit Singh [view email] [v1] Wed, 25 Mar 2026 08:21:08 UTC (305 KB) Access Paper: HTML (experimental) view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-03 Change to browse by: physics physics.optics References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)