arXiv subjects

Guilherme L. Zanin

Publications and source records attributed to Guilherme L. Zanin.

5 recordsLinked to original sources

arXiv2026

Hyperentanglement in intermediate phase-space planes: benchmarking a photon-pair source for quantum key distribution

We characterize a source of photon pairs simultaneously entangled in polarization and in the transverse spatial degree of freedom, with the spatial measurements performed in intermediate planes of the fractional Fourier transform. The source consists of two crossed type-I crystals in a non-collinear geometry, such that the transverse variables carry information about the crystal of origin. Detection in the crystal plane reveals this information completely and destroys the polarization entanglement, so that a scheme using the near and far fields as conjugate spatial bases cannot support a parallel polarization channel. In intermediate planes both spatial bases combine position and momentum, such that the which-crystal information is partially erased, and the polarization entanglement survives in all four combinations of spatial bases. Applying Bell and Einstein-Podolsky-Rosen criteria to the same photon pairs certifies both degrees of freedom simultaneously. We evaluate quantum bit error rates and asymptotic secret key rates in each degree of freedom, and find that the source delivers two simultaneously usable channels per photon pair.

quant-ph↗

arXiv2026

Structured light under turbulence

Structured light has emerged as a promising resource for high-capacity and secure free-space optical communication, where atmospheric turbulence remains a major source of signal degradation. In this work, we investigate the resilience of different transverse mode structures of an optical beam with respect to the random action of turbulence. A spatial light modulator (SLM) is programmed to apply amplitude and phase modulation corresponding to the desired transverse mode, which is then transmitted through a turbulent medium emulated by a second SLM. Laguerre-Gauss, Hermite-Gauss, and Airy beams are investigated through the resulting intensity distributions measured with a camera. Different figures of merit are used to evaluate and compare the resilience of these modes.

physics.optics↗

arXiv2024

Optical Algorithm for Derivative of Real-Valued Functions

The derivation of a function is a fundamental tool for solving problems in calculus. Consequently, the motivations for investigating physical systems capable of performing this task are numerous. Furthermore, the potential to develop an optical computer to replace conventional computers has led us to create an optical algorithm and propose an experimental setup for implementing the derivative of one-dimensional real-valued functions using a paraxial and monochromatic laser beam. To complement the differentiation algorithm, we have experimentally implemented a novel optical algorithm that can transfer a two-dimensional phase-encoded function to the intensity profile of a light beam. Additionally, we demonstrate how to implement the n-th derivative of functions encoded in the phase of the transverse profile of photons.

physics.optics↗

arXiv2024

Multimode Squeezed State for Reconfigurable Quantum Networks at Telecommunication Wavelengths

Continuous variable encoding of quantum information requires the deterministic generation of highly correlated quantum states of light in the form of quantum networks, which, in turn, necessitates the controlled generation of a large number of squeezed modes. In this work, we present an experimental source of multimode squeezed states of light at telecommunication wavelengths. Generation at such wavelengths is especially important as it can enable quantum information processing, communication, and sensing beyond the laboratory scale. We use a single-pass spontaneous parametric down-conversion process in a non-linear waveguide pumped with the second harmonic of a femtosecond laser. Our measurements reveal significant squeezing in more than 21 frequency modes, with a maximum squeezing value exceeding 2.5 dB. We demonstrate multiparty entanglement by measuring the state's covariance matrix. Finally, we show the source reconfigurability by preparing few-node cluster states and measure their nullifier squeezing level. These results pave the way for a scalable implementation of continuous variable quantum information protocols at telecommunication wavelengths, particularly for multiparty, entanglement-based quantum communications. Moreover, the source is compatible with additional pulse-by-pulse multiplexing, which can be utilized to construct the necessary three-dimensional entangled structures for quantum computing protocols.

quant-ph↗

arXiv2022

Enhanced Photonic Maxwell's Demon with Correlated Baths

Maxwell's Demon is at the heart of the interrelation between quantum information processing and thermodynamics. In this thought experiment, a demon generates a temperature gradient between two thermal baths initially at equilibrium by gaining information at the single-particle level and applying classical feed-forward operations, allowing for the extraction of work. Here we implement a photonic version of Maxwell's Demon with active feed-forward in a fibre-based system using ultrafast optical switches. We experimentally show that, if correlations exist between the two thermal baths, the Demon can generate a temperature difference over an order of magnitude larger than without correlations, and so extract more work. Our work demonstrates the great potential of photonic experiments -- which provide a unique degree of control on the system -- to access new regimes in quantum thermodynamics.

quant-ph↗