Explanipedia

A Mobile Impurity in the Kitaev Chain: Phase Diagram and Signatures of Topology Open

А. V. Sadovnikov, M. S. Bahovadinov, A. N. Rubtsov, A. A. Markov · 2025

We study the physics of a mobile impurity immersed in a $1d$ topological superconductor. We discuss the system's phase diagram obtained with exact diagonalization. We argue that the character of the transition from a weak to strong couplin…

Progress in the development of quantum algorithms and software Open

Anastasiia S. Nikolaeva, Daria O. Konina, A. V. Antipov, Maxim A. Gavreev, Konstantin M. Makushin , et al. · 2025

A quantum processor, like any computing device, requires the development of both hardware and the necessary set of software solutions, starting with quantum algorithms and ending with means of accessing quantum devices. As part of the road…

Mean field decoupling of single impurity Anderson model through auxiliary Majorana fermions Open

Irakli Titvinidze, Julian Stobbe, A. N. Rubtsov, G. Rohringer · 2025

We present a method to study the time evolution of the single impurity Anderson model which exploits a mean field decoupling of the interacting impurity and the non-interacting bath (in form of a chain). This is achieved by the introductio…

Locality of topological dynamics in Chern insulators Open

A. A. Markov, Diana Golovanova, Alexander R. Yavorsky, A. N. Rubtsov · 2024

A system having macroscopic patches in different topological phases has no well-defined global topological invariant. To treat such a case, the quantities labeling different areas of the sample according to their topological state are used…

Fluctuating field series: towards calculations of correlated systems with high accuracy Open

Yana S. Lyakhova, S. D. Semenov, A. I. Lichtenstein, A. N. Rubtsov · 2024

We introduce regular series expansion for weakly- and moderately-correlated fermionic systems, based on Fluctuating Local Field approach. The method relies on the explicit account of leading fluctuating mode(s) and is therefore suitable fo…

Classical Modeling of a Lossy Gaussian Bosonic Sampler Open

Mikhail V. Umanskii, A. N. Rubtsov · 2024

Gaussian boson sampling (GBS) is considered a candidate problem for demonstrating quantum advantage. We propose an algorithm for the approximate classical simulation of a lossy GBS instance. The algorithm relies on the Taylor series expans…

Mean Field Decoupling of Single Impurity Anderson Model through Auxiliary Majorana Fermions Open

Irakli Titvinidze, Julian Stobbe, A. N. Rubtsov, G. Rohringer · 2024

We present a method to study the time evolution of the single impurity Anderson model which exploits a mean field decoupling of the interacting impurity and the non-interacting bath (in form of a chain). This is achieved by the introductio…

Design of vortex apparatus for gas cleaning and investigation of its efficiency Open

Vitaly Afanasenko, A. N. Rubtsov, Peter Kulakov, Evgeniy Boev, Z R Mukhametzyanov · 2024

Purification of gas streams from inhomogeneous impurities is widely used in the chemical and oil industries. One of the most popular methods is separation of mixtures by centrifugal forces in a twisted flow. The article presents the design…

Towards out of equilibrium impurity solver for the Dynamical Mean Field Theory Open

А. В. Карпов, G. Sultanov, Evgeny Polyakov, A. N. Rubtsov · 2023

The Dynamical Mean Field Theory (DMFT) is a powerful tool for calculating highly correlated systems (both bosonic and fermionic) in a state of thermodynamic equilibrium. However, in the case of non-equilibrium states, the method has signif…

Landau Free Energy of small clusters beyond mean field approach Open

Semen N. Semenov, A. N. Rubtsov · 2023

The Landau Free Energy determines the landscape of order parameter fluctuations that occur in a physical system at thermal equilibrium and, in particular, characterizes the critical phenomena. We propose a semi-analytical approach based on…

Locality of topological dynamics in Chern insulators Open

A. A. Markov, Diana Golovanova, A. R. Yavorsky, A. N. Rubtsov · 2023

A system having macroscopic patches in different topological phases have no well-defined global topological invariant. To treat such a case, the quantities labeling different areas of the sample according to their topological state are use…

Coherent control of symmetry breaking in transverse-field Ising chains using few-cycle pulses Open

Nikolai D. Klimkin, A. N. Rubtsov, Misha Ivanov · 2023

Coherent control of quantum systems with phase-stable pulses offers enticing new opportunities for lightwave electronics. Here we extend this approach to many-body systems with spin degrees of freedom, demonstrating that a single few-cycle…

Classical Modelling of a Bosonic Sampler with Photon Collisions Open

Mikhail V. Umanskii, A. N. Rubtsov · 2023

The original formulation of the boson sampling problem assumed that little or no photon collisions occur. However, modern experimental realizations rely on setups where collisions are quite common, i.e., the number of photons M injected in…

Fluctuating local field method for the disordered Ising model Open

Daria Kuznetsova, Grigory V. Astretsov, A. N. Rubtsov · 2022

We present a method for computing thermal properties of classical spin clusters with arbitrarily chosen interactions between spins. For such systems, instability channels are \textit{a priori} not known. The method is based on the Fluctuat…

Dynamical Quantum Phase Transition Without An Order Parameter Open

O. N. Kuliashov, A. A. Markov, A. N. Rubtsov · 2022

Short-time dynamics of many-body systems may exhibit non-analytical behavior of the systems' properties at particular times, thus dubbed dynamical quantum phase transition. Simulations showed that in the presence of disorder new critical t…

Mean-field concept and post-DMFT methods in the modern theory of correlated systems Open

Yana S. Lyakhova, Grigory V. Astretsov, A. N. Rubtsov · 2022

On the question of measurement in quantum mechanics Open

A. N. Rubtsov · 2022

Truly local topological dynamics of driven defects in Chern insulator Open

Diana B. Golovanova, Alexander R. Yavorsky, A. A. Markov, A. N. Rubtsov · 2021

Robust zero modes supported by defects is one of the key features of topological matter. Its presence renders a system topologically inhomegeneuous, thus having no well-defined global topological invariant. The quantities labeling differen…

Local marker for interacting topological insulators Open

A. A. Markov, A. N. Rubtsov · 2021

Topological states of matter were first introduced for non-interacting\nfermions on an infinite uniform lattice. Since then, substantial effort has\nbeen made to generalize these concepts to more complex settings. Recently,\nlocal markers …

Quantum Monte Carlo simulation of BEC-impurity tunneling Open

A. S. Popova, V. V. Tiunova, A. N. Rubtsov · 2021

Polaron tunneling is a prominent example of a problem characterized by different energy scales, for which the standard quantum Monte Carlo methods face a slowdown problem. We propose a new quantum-tunneling Monte Carlo (QTMC) method which …

Fluctuating local field approach to free energy of 1D molecules with strong collective electronic correlations Open

Yana S. Lyakhova, E. A. Stepanov, A. N. Rubtsov · 2021

The impact of leading collective electronic fluctuations on a free energy of a prototype 1D model for molecular systems is considered within the recently developed Fluctuating Local Field (FLF) approach. The FLF method is a non-perturbativ…

Transient optical non-linearity in p-Si induced by a few cycle extreme THz field Open

A. B. Savel’ev, O. V. Chefonov, А. В. Овчинников, A. N. Rubtsov, A. P. Shkurinov , et al. · 2021

We study the impact of a few cycle extreme terahertz (THz) radiation (the field strength E THz ∼1–15 MV/cm is well above the DC-field breakdown threshold) on a p -doped Si wafer. Pump-probe measurements of the second harmonic of a weak inf…

Collective magnetic fluctuations in Hubbard plaquettes captured by fluctuating local field method Open

A. N. Rubtsov, E. A. Stepanov, A. I. Lichtenstein · 2020

We establish a way to handle main collective fluctuations in correlated\nquantum systems based on a Fluctuation Local Field concept. This technique goes\nbeyond standard mean-field approaches, such as Hartree-Fock and dynamical\nmean-field…

Dual fermion method as a prototype of generic reference-system approach for correlated fermions Open

Sergey Brener, E. A. Stepanov, A. N. Rubtsov, M. I. Katsnelson, A. I. Lichtenstein · 2020

Quantum Monte-Carlo simulation of polaron tunneling Open

A. S. Popova, V. V. Tiunova, A. N. Rubtsov · 2020

Polaron tunneling is a prominent example of a task with the different energy scales, for which using the standard quantum Monte-Carlo methods faces a slow-down problem. We construct a path-integral quantum Monte-Carlo method which is free …

Local marker for topological insulators beyond equilibrium non-interacting systems Open

A. A. Markov, A. N. Rubtsov · 2020

Local topological markers appear to be a powerful tool in the studies of topological matter allowing to treat inhomogeneous systems. To the best of our knowledge no local marker for interacting matter itself, without a reference non-intera…

Dual parquet scheme for the two-dimensional Hubbard model: Modeling low-energy physics of high- cuprates with high momentum resolution Open

Grigory V. Astretsov, G. Rohringer, A. N. Rubtsov · 2020

We present a new method to treat the two-dimensional (2D) Hubbard model for\nparameter regimes which are relevant for the physics of the high-$T_c$\nsuperconducting cuprates. Unlike previous attempts to attack this problem, our\nnew approa…

Effectively Trainable Semi-Quantum Restricted Boltzmann Machine Open

Yana S. Lyakhova, Evgeny Polyakov, A. N. Rubtsov · 2020

We propose a novel quantum model for the restricted Boltzmann machine (RBM), in which the visible units remain classical whereas the hidden units are quantized as noninteracting fermions. The free motion of the fermions is parametrically c…

Attosecond spectral singularities in solid-state high-harmonic generation Open

Ayelet J. Uzan, Gal Orenstein, Álvaro Jiménez-Galán, Chris McDonald, Rui E. F. Silva , et al. · 2020

Dual boson approach with instantaneous interaction Open

L. Peters, Erik G. C. P. van Loon, A. N. Rubtsov, A. I. Lichtenstein, M. I. Katsnelson , et al. · 2019

The Dual Boson approach to strongly correlated systems generally involves a\ndynamic (frequency-dependent) interaction in the auxiliary impurity model. In\nthis work, we explore the consequences of forcing this interaction to be\ninstantan…

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