arXiv subjects

Andrzej Gajewski

Publications and source records attributed to Andrzej Gajewski.

5 recordsLinked to original sources

arXiv2026

Autonomous Optical Alignment of Satellite-Based Entanglement Sources using Reinforcement Learning

Quantum entanglement distributed via satellites enable global-scale quantum communication. However, onboard sources are susceptible to misalignment due to dynamical orbital conditions. Here, we present two recalibration techniques for efficient generation of high quality entanglement using a periodically poled lithium niobate (PPLN)-based spontaneous parametric down-conversion (SPDC) source with minimum intervention. The first is a heuristic algorithm (HA) which mimics the manual alignment process in a laboratory. The second is based on reinforcement learning (RL). Our simulation demonstrates superior performance of RL with AUC=0.9119 compared to HA's 0.7042 in the modified ROC analysis (60 min threshold). RL achieves perfect alignment in 10 min as opposed to HA's 30 min. Both the methods operate within feasible satellite constraints, offering scalable automation for complex quantum communication scenarios.

quant-ph↗

arXiv2022

Light guided in tailored environments: from basic aspects to applications (Ph.D. thesis)

This dissertation is dedicated to investigating quantum optical effects involving single photons in tailored structures. It consists of six chapters and an appendix. The central part of the thesis starts with a chapter titled "Theoretical background" where the author introduces key quantum optical concepts needed for understanding the subsequent chapters. The next chapter is devoted to a discussion of the estimation of the Sellmeier coefficient in nonlinear crystals with the SPDC process. The accuracy and feasibility of the method are analysed in the context of the experimental results. The subsequent chapter is focused on the numerical modelling of the photon pair wavefunction generated in the SPDC process. In this chapter, the author presented a comparison between numerically predicted outcomes with the experimental results obtained in two different laboratory setups. The fifth chapter is devoted to modelling the modes of the bent waveguide, combining analytical considerations and numerical modelling. The correctness of the results is verified with numerical simulations obtained in COMSOL. In this chapter author emphasized the context of basic research: It is shown that the bent waveguide is described by equations analogous to the equations of the dynamics of a quantum particle in a space with axial symmetry. The appendix is devoted to the form of the differential operator in cylindrical coordinates, the analysis of the influence of photon propagation in the optical fibre on the photon wave function and the Schrödinger equation for a particle in two-dimensional space with axial symmetry.

quant-ph↗

arXiv2020

Waveguide platform for quantum anticentrifugal force

This work is a proposal for an experimental platform to observe quantum fictitious anticentrifugal force. We present an analytical and numerical treatment of a rectangular toroidal dielectric waveguide. Solving the Helmholtz equation we obtain analytical solutions for transverse spatial modes and estimate their number as a function of system characteristics. On top of that, the analysis of the structure was extended onto a real material platform, a thin film lithium niobate on an insulator rib waveguide. The framework presented here can be directly applied to analyze the phenomenon of quantum anti-centrifugal force.

quant-ph↗

arXiv2017

Dispersion measurement method with down conversion process

Proper characterization of nonlinear crystals is essential for designing single photon sources. We show a technique for dispersion characterization of a nonlinear material by making use of phase matching in the process of parametric down conversion. Our method is demonstrated on an exemplary periodically poled potassium titanyl phosphate $KTiOPO_4$ crystal phase-matched for $396$ nm to $532$ nm and $1550$ nm. We show a procedure to characterize the dispersion in the range of $390$ to $1800$ nm by means of only one spectrometer for the UV-visible range.

physics.optics↗

arXiv2015

Spectral correlation in down-converted photon pairs at telecom wavelength

Sources of photon pairs based on the spontaneous parametric down conversion process are commonly used for long distance quantum communication. The key feature for improving the range of transmission is engineering their spectral properties. Following two experimental papers [Opt. Lett., 38, 697 (2013)] and [Opt. Lett., 39, 1481 (2014)] we analytically and numerically analyze the characteristics of a source. It is based on a $β$-barium borate (BBO) crystal cut for type II phase matching at the degenerated frequencies 755 nm $\rightarrow$ 1550 nm + 1550 nm. Our analysis shows a way for full control of spectral correlation within a fiber-coupled photon pair simultaneously with optimal brightness.

quant-ph↗