arXiv subjects

Simón Paiva-Ortega

Publications and source records attributed to Simón Paiva-Ortega.

3 recordsLinked to original sources

arXiv2026

QuDPy-FDGF: A Python-Based Tool for Computing Ultrafast Nonlinear Optical Responses Using Frequency Domain Green's Functions

We present QuDPy-FDGF, an open-source Python framework that evaluates Liouville-space pathways as hybrid chains of time propagators and frequency-domain Green's functions. Frequency-resolved intervals are computed directly through shifted linear systems, without time propagation followed by a Fourier transform, while other intervals may remain in the time domain. A model-agnostic block interface separates the physical model from pathway construction, numerical propagation, and detection. The released implementation provides an explicit dense Liouville-space backend for reference calculations and a sector-resolved sparse backend using matrix-free generator actions, Krylov time propagation, and generalized minimal residual (GMRES) resolvent solves. Its observable layer reuses propagated pathway responses to evaluate operator expectation values, action-detected readout interactions, instantaneous jump rates, and integrated mean jump counts. The framework is assessed on an analytically solvable open two-level system and on two examples of increasing complexity: the complete third-order rephasing response, with its eight sequences, of a thermally initialized anisotropic Heisenberg (XXZ) spin chain with unequal excitation sectors, and two coupled dissipative anharmonic modes whose spectra depend on the detected observable, with the fifth-order double-quantum response of their closed limit. The calculations reproduce the analytical two-level response, check the matrix-free sparse evaluation against the dense assembly of the generator, and recover the harmonic-limit cancellation of the fifth-order signal when the required three-excitation manifold is retained. QuDPy-FDGF therefore provides a unified framework for pathway- and observable-resolved nonlinear spectroscopy in finite or truncated Hilbert spaces with unitary or Markovian Gorini--Kossakowski--Sudarshan--Lindblad (GKSL) dynamics.

physics.chem-ph↗

arXiv2026

Bottom-Up Design of Quantum Optical Experiments Using Discrete Generative Models

Designing quantum optical experiments requires searching over discrete circuit topologies and continuous parameters, often with multiple realizations of the same target state. Graph-based methods commonly address this problem by optimizing a dense graph and pruning it toward a single circuit. We introduce \texttt{Grinch}, a bottom-up reward-driven generative framework that learns to sample optical graphs directly from fidelity-based rewards without relying on a pre-existing training dataset. We demonstrate the framework on multipartite entangled states, graph and cluster states, and nonlocal photonic-gate targets, obtaining multiple high-fidelity optical graphs. We identify asymptotic solutions for states that cannot be generated exactly by graphs, as well as nonlocal Toffoli gate constructions requiring two ancillas. Our work presents hardware-constraint objectives, which lead to alternative constructions of CNOT and Toffoli gates when connections between ancilla nodes are restricted. These findings illustrate a reward-driven approach to quantum optical inverse design, exploring alternative circuit topologies while directly incorporating connectivity constraints into the search process.

quant-ph↗

arXiv2026

Detection Defines Dephasing in Two-Dimensional Electronic Spectroscopy of Materials: Coherent Field Emission versus Incoherent Population Observables

The homogeneous spectral linewidth associated with light-matter interactions is a fundamental descriptor of the optical properties of materials, governed by the quantum dynamics of the condensed-matter system. We discuss here that the homogeneous linewidth measured by means of two-dimensional electronic spectroscopy depends not only on the intrinsic microscopic dynamics of the material, but also on the observable through which those dynamics are projected onto the measurement. In this Perspective, we develop a unified framework showing that identical microscopic dynamics can yield different experimentally inferred dephasing times because different detection operators project different sectors of the nonequilibrium dynamics. For coherent emitted-field measurements, the observed linewidth largely retains its conventional connection to the optical coherence time $T_2$. By contrast, in population-detected modalities such as photoluminescence, photocurrent, and other action-detected two-dimensional spectroscopies, the apparent linewidth can additionally encode excited-state population redistribution dynamics, leading naturally to an effective coherence time $T_{2,\mathrm{eff}}$. Using a coupled-mode model propagated under a common Liouvillian, we show that identical microscopic dynamics yield distinct apparent dephasing times when projected onto coherent-emission and population-derived observables. The detection observable is therefore not merely part of the experimental implementation, but determines what dynamical information remains experimentally observable and how homogeneous linewidths should be interpreted as materials descriptors.

physics.chem-ph↗