Publications Tatiana VOVK

2025

T. Vovk, A. Van de Walle, H. Pichler, A. Bohrdt Neural quantum states for emitter dynamics in waveguide QED, (2025-08-12), arXiv:2508.08964 arXiv:2508.08964 (ID: 721504) Toggle Abstract
Quantum emitters coupled to one-dimensional waveguides constitute a paradigmatic quantum-optical platform for exploring collective phenomena in open quantum many-body systems. For appropriately spaced emitters, they realize the Dicke model, whose characteristic permutation symmetry allows for efficient exact solutions featuring superradiance. When the emitters are arbitrarily spaced, however, this symmetry is lost and general analytical solutions are no longer available. In this work, we introduce a novel numerical method to study the dynamics of such systems by extending the time-dependent neural quantum state (t-NQS) framework to open quantum systems. We benchmark our approach across a range of waveguide QED settings and compare its performance with tensor-network calculations. Our results demonstrate that the t-NQS approach is competitive with other numerical methods and highlight the potential of t-NQSs for studying open quantum many-body systems out of equilibrium.

T. Vovk, H. Pichler Quantum trajectory entanglement in various unravelings of Markovian dynamics, Phys. Rev. A 110 12207 (2024-07-08), http://dx.doi.org/10.1103/PhysRevA.110.012207 doi:10.1103/PhysRevA.110.012207 (ID: 721269) Toggle Abstract
The cost of classical simulations of quantum many-body dynamics is often determined by the amount of entanglement in the system. In this paper, we study entanglement in stochastic quantum trajectory approaches that solve master equations describing open quantum system dynamics. First, we introduce and compare adaptive trajectory unravelings of master equations. Specifically, building on [Phys. Rev. Lett. 128, 243601 (2022)], we study several greedy algorithms that generate trajectories with a low average entanglement entropy. Second, we consider various conventional unravelings of a one-dimensional open random Brownian circuit and locate the transition points from area- to volume-law-entangled trajectories. Third, we compare various trajectory unravelings using matrix product states with a direct integration of the master equation using matrix product operators. We provide concrete examples of dynamics, for which the simulation cost of stochastic trajectories is exponentially smaller than the one of matrix product operators.

T. Vovk, Hannes Pichler Entanglement-Optimal Trajectories of Many-Body Quantum Markov Processes, Phys. Rev. Lett. 128 243601 (2022-06-13), http://dx.doi.org/10.1103/PhysRevLett.128.243601 doi:10.1103/PhysRevLett.128.243601 (ID: 720844) Toggle Abstract
We develop a novel approach aimed at solving the equations of motion of open quantum many-body systems. It is based on a combination of generalized wave function trajectories and matrix product states. We introduce an adaptive quantum stochastic propagator, which minimizes the expected entanglement in the many-body quantum state, thus minimizing the computational cost of the matrix product state representation of each trajectory. We illustrate this approach on the example of a one-dimensional open Brownian circuit. We show that this model displays an entanglement phase transition between area and volume law when changing between different propagators and that our method autonomously finds an efficiently representable area law unraveling.