arXiv subjects

I. V. Vovchenko

Publications and source records attributed to I. V. Vovchenko.

6 recordsLinked to original sources

arXiv2026

Kaleidoscopic-ray-tracing-based model of the scintillation flash energy deposition in the photomultipliers attached to a strip scintillator

Strip scintillator detectors are used nowadays in many fields of applied physics, particularly in medicine, civil engineering, mapping of underground resources, and security. In this work we provide an analytical description of light transport in a cuboid-shaped strip scintillator detector from the scintillation location to the detecting surface. We use kaleidoscopic-ray-tracing approach to reproduce the average time profile of the energy deposition (light collection) in the detecting surface. We demonstrate the applicability of the model on the case of PWO crystal of $1.5\times 1.5 \times 30$ cm$^3$ size. We show that the results achieved in the model are in good agreement with Monte Carlo (MC) simulation. Notably, the developed model requires dozens of milliseconds to be implemented, thus, it is applicable for real-time calibration of the detector, while the MC simulation takes hours. Also, we highlight that the kaleidoscopic-ray-tracing itself being used in MC simulations can highly speed them up in the case of specular reflectors.

physics.ins-det↗

arXiv2026

Thermodynamic coprocessor for linear operations with input-size-independent calculation time based on open quantum system

Linear operations, e.g., vector-matrix and vector-vector multiplications, are core operations of modern neural networks. To diminish computational time, these operations are implemented by parallel computations using different coprocessors. In this work we show that an open quantum system consisting of bosonic modes and interacting with bosonic reservoirs can be used as an analog thermodynamic coprocessor implementing multiple vector-matrix multiplications with stochastic matrices in parallel. Input vectors are encoded in occupancies of reservoirs, and the output result is presented by stationary energy flows. The operation takes time needed for the system's transition to a non-equilibrium stationary state independently on the number of the reservoirs, i.e., on the input vector dimension. With technological limitations being considered, a device of $5\times5$ cm$^2$ area covered with the coprocessors can conduct of the order of $10^{11}$ operations per second per a mode of the OQS. The computations are accompanied by an entropy growth. We construct a direct mapping between open quantum systems and electrical crossbar structures frequently used in analog vector-matrix multiplication, showing that dissipation rates multiplied by open quantum system's modes frequencies can be seen as conductivities, reservoirs' occupancies can be seen as potentials, and stationary energy flows can be seen as electric currents.

quant-ph↗

arXiv2026

Measurement-based acceleration of optical computations

Analog coprocessors are intensively developing nowadays with the aim to optimize energy computations of neural networks. In this work we focus on the possibility of using detection of collective oscillations in optical systems for computational purposes. We show that in a system of coupled resonators, collective oscillations can be used to implement matrix-vector multiplication. The matrix is formed by the coupling constants between the resonators, and the input vector is formed by the initial occupancies of the involved modes. The frequency of the collective oscillations is growing with the number of the involved modes, similarly to Rabi oscillations. The time needed for their detection, i.e., averaging, decreases with an increase in the input vector dimension. We discuss the limitations imposed on parallel computation in the system by restriction of the allowed optical frequency band.

physics.optics↗

arXiv2025

Optical coprocessor based on spontaneous Brillouin scattering

Analog coprocessors for neural networks are an intensively developing field. They provide approximate results of computations for relatively low energy cost and at high speed. We show that a set of ring resonators with Brillouin interaction between photons and phonons, being coupled to a waveguide, can be used to implement matrix-vector multiplication. The input vector is formed by occupancies of the anti-Stokes optical modes pumped via spontaneous Brillouin scattering, i.e, scattering on thermal phonons. Brillouin scattering rates and coupling constants between ring resonators and the waveguide form the matrix. The system allows for parallel computations in frequency band.

physics.optics↗

arXiv2024

Second-law-allowed temporal cooling of the coldest reservoir without external refrigeration

Non-equilibrium quantum thermodynamics is an intensively developing field with many existing applications. We study the dynamics of temperatures and chemical potentials of fermionic reservoirs coupled to an open quantum system. We show that heat transfer from the coldest reservoir to the hottest one is allowed by the Clausius inequality and results in transient cooling of the coldest reservoir without additional external refrigeration. We show that during the establishment of thermal and chemical equilibrium, non-monotone evolution of reservoirs' temperatures and chemical potentials is possible, including changes in reservoirs' temperatures and chemical potentials orderliness. Achieved results can be used in the design of quantum thermal machines and nanoelectronic devices.

quant-ph↗

arXiv2023

Transient Temperature Dynamics of Reservoirs Connected Through an Open Quantum System

The dynamics of open quantum systems connected with several reservoirs attract great attention due to its importance in quantum optics, biology, quantum thermodynamics, transport phenomena, etc. In many problems, the Born approximation is applicable which implies that the influence of the open quantum system on the reservoirs can be neglected. However, in the case of a long-time dynamics or mesoscopic reservoir, the reverse influence can be crucial. In this paper, we investigate the transient dynamics of several bosonic reservoirs connected through an open quantum system. We use an adiabatic approach to study the temporal dynamics of temperatures of the reservoirs during relaxation to thermodynamic equilibrium. We show that there are various types of temperature dynamics that strongly depend on the values of dissipative rates and initial temperatures. We demonstrate that temperatures of the reservoirs can exhibit non-monotonic behavior. Moreover, there are moments of time during which the reservoir with initially intermediate temperature becomes the hottest or coldest reservoir. The obtained results pave the way for managing energy flows in mesoscale and nanoscale systems.

quant-ph↗