Towards Schrödinger Cat States in the Second Harmonic Generation

• URL: http://arxiv.org/abs/2603.24067v2
• Date: Wed, 01 Apr 2026 11:16:20 GMT
• Title: Towards Schrödinger Cat States in the Second Harmonic Generation
• Abstract summary: We investigate the quantum evolution of the pump field in second-harmonic generation under strong pump depletion.<n>The pump develops a nonclassical phase-space structure resembling a Schrdinger cat state.<n>The results indicate that nonlinear frequency conversion can generate macroscopic superposition-like states of the pump field.
• Score: 0.1749935196721634
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: 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.

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