arXiv subjects

Romaric Journet

Publications and source records attributed to Romaric Journet.

4 recordsLinked to original sources

arXiv2026

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

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 $α= 2.47$, 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 $\propto \hat{S}(z)(|α\rangle - |-α\rangle)$, with $α= 2.47$ 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.

quant-ph↗

arXiv2025

Fast, accurate, and predictive method for atom detection in site-resolved images of microtrap arrays

We introduce a new method, rooted in estimation theory, to detect individual atoms in site-resolved images of microtrap arrays, such as optical lattices or optical tweezers arrays. Using labelled test images, we demonstrate drastic improvement of the detection accuracy compared to the popular method based on Wiener deconvolution when the inter-site distance is comparable to the radius of the point spread function. The runtime of our method scales approximately linearly with the number of sites, and remains well below 100 ms for an array of 100 x 100 sites on a desktop computer. It is therefore fully compatible with a real-time usage. Finally, we propose a rigorous definition for the signal-to-noise ratio of the problem, and show that it can be used as a predictor for the detection error rate. Our work opens the prospect for future experiments with increased array sizes, or reduced inter-site distances.

quant-ph↗

arXiv2024

Differential polarizability at 1064 nm of the strontium intercombination transition

We measure the scalar, vector and tensor components of the differential dynamic polarizability of the strontium intercombination transition at 1064 nm. We compare the experimental values with the theoretical prediction based on the most recently published spectroscopic data, and find a very good agreement. We also identify a close-to-circular `magic' polarization where the differential polarizability strictly vanishes, and precisely determine its ellipticity. Our work opens new perspectives for laser cooling optically trapped strontium atoms, and provides a new benchmark for atomic models in the near infrared spectral range.

physics.atom-ph↗

arXiv2024

Experimental demonstration of a versatile and scalable scheme for iterative generation of non-Gaussian states of light

Non-Gaussian states of light, such as GKP states, are essential resources for optical continuous-variable quantum computing. The ability to efficiently produce these states would open up tremendous prospects for quantum technologies in general and fault-tolerant quantum computing in particular. This letter demonstrates a versatile method using a quantum memory cavity to overcome the probabilistic nature of the breeding protocols and generate non-Gaussian states at high rates with scalability perspectives. The performances of our experimental setup are illustrated with the generation of Schrödinger cat states of amplitude alpha = 1.63 with a fidelity of more than 60% at a generation rate in the kHz range, which is higher than the state of the art for such states.

quant-ph↗