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arXiv · 2601.09672

Generation of Large Coherent-State Superpositions in Free-Space Optical Pulses

Lucas Caron·Hector Simon·Hugo Basset·Romaric Journet·Rosa Tualle-Brouri
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Abstract

The generation of non-Gaussian quantum states is a key requirement for universal continuous-variable quantum information processing. We report the experimental generation of large-amplitude squeezed coherent-state superpositions (squeezed cat states) on free-space optical pulses, reaching an amplitude of $\alpha = 2.47$, which, to our knowledge, exceeds all previously reported values. Our protocol relies on the controlled mixing of the Fock states $|1\rangle$ and $|2\rangle$ through a tunable beam splitter, followed by heralding via homodyne detection. The resulting state displays three well-resolved negative regions in its Wigner function and achieves a fidelity of $0.53$ with the target state $\propto \hat{S}(z)(|\alpha\rangle - |-\alpha\rangle)$, with $\alpha = 2.47$ and squeezing parameter $z = 0.56$. These results constitute a significant milestone for temporal breeding protocols and for the iterative generation of optical GKP states, opening new perspectives for scalable and fault-tolerant photonic quantum architectures.

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Lucas Caron, Hector Simon, Hugo Basset, Romaric Journet, Rosa Tualle-Brouri. 2026-01-14. Generation of Large Coherent-State Superpositions in Free-Space Optical Pulses. https://arxiv.org/abs/2601.09672

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