arXiv subjects

Jan Dragašević

Publications and source records attributed to Jan Dragašević.

4 recordsLinked to original sources

arXiv2026

The subthreshold issue of fusion-based quantum computing

Fusion-based quantum architectures are the leading approach to photonic quantum computing. However, the sub-threshold regime, where logical error rates must reach the levels required by useful applications, has received little attention. We show that in this regime, fusion failure imposes a noise floor on the logical error rate that prevents all-linear-optics architectures from reaching the required rates at low overhead. For fusion-based architectures using quantum emitter spins, we show that the noise floor is reduced by orders of magnitude at a lower overhead.

quant-ph↗

arXiv2025

Viscous heat backflow and temperature resonances in extreme thermal conductors

We demonstrate that non-diffusive, fluid-like heat transport, such as heat backflowing from cooler to warmer regions, can be induced, controlled, and amplified in extreme thermal conductors such as graphite and hexagonal boron nitride. We employ the viscous heat equations, i.e., the thermal counterpart of the Navier-Stokes equations in the laminar regime, to show with first-principles quantitative accuracy that a finite thermal viscosity yields steady-state heat vortices, and governs the magnitude of transient temperature waves. Finally, we devise strategies that exploit devices' boundaries and resonance to amplify and control heat hydrodynamics, paving the way for novel experiments and applications in next-generation electronic and phononic technologies.

cond-mat.mtrl-sci↗

arXiv2025

Weighing the curvature invariants

We prove several inequalities between the curvature invariants, which impose constraints on curvature singularities. Some of the inequalities hold for a family of spacetimes which include static, Friedmann--Lemaître--Robertson--Walker, and Bianchi type I metrics, independently of whether they are solutions of some particular field equations. In contrast, others hold for solutions of Einstein's gravitational field equation and a family of energy-momentum tensors (featuring ideal fluids, scalar fields and nonlinear electromagnetic fields), independently of the specific form of the spacetime metric. We illustrate different behaviour of the basic curvature invariants with numerous examples and discuss the consequences and limitations of the proven results.

gr-qc↗

arXiv2024

Tunnelling of a composite particle in presence of a magnetic field

We present a simple model of composite particle tunnelling through a rectangular potential barrier in presence of magnetic field. The exact numerical solution of the problem is provided and the applicability to real physical situations is discussed. Some qualitative features of tunnelling with no magnetic interaction are retained, but some new ones are also observed. The resonance peaks in transmission spectrum generally do not reach $100\%$ transmission probability when the magnetic field is turned on. We observe splitting and in some cases widening of transmission probability peaks. When the width $b$ of area with magnetic field is large, we observe oscillations of spin-flip probability with energy and $b$ which are caused by Larmor precession of spin about the vector of magnetic field. For some values of relevant parameters we also observe significant increase of tunnelling probability for low energies in the single particle case.

quant-ph↗