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Density matrices are powerful mathematical tools for the description of closed and open quantum systems. Recently, methods for the direct computation of density matrix elements in scalar quantum field theory were developed based on thermo…

High Energy Physics - Theory · Physics 2025-03-12 Christian Käding , Mario Pitschmann

We find dynamical invariants for open quantum systems described by the non-Markovian quantum state diffusion (QSD) equation. In stark contrast to closed systems where the dynamical invariant can be identical to the system density operator,…

Quantum Physics · Physics 2016-04-29 Da-Wei Luo , P. V. Pyshkin , Chi-Hang Lam , Ting Yu , Hai-Qing Lin , J. Q. You , Lian-Ao Wu

We provide a versatile analytical framework for calculating the dynamics of a spin system in contact with a fermionic bath beyond the Markov approximation. The approach is based on a second order expansion of the Nakajima-Zwanzig master…

Mesoscale and Nanoscale Physics · Physics 2019-10-18 Stephanie Matern , Daniel Loss , Jelena Klinovaja , Bernd Braunecker

We study the quantum dynamics of conversion of composite bosons into fermionic fragment species with increasing densities of bound fermion pairs using the open quantum system approach. The Hilbert space of $N$-state-function is decomposed…

Quantum Physics · Physics 2013-04-12 A. Thilagam

We treat several key stochastic equations for non-Markovian open quantum system dynamics and present a formalism for finding solutions to them via canonical perturbation theory, without making the Born-Markov or rotating wave approximations…

Quantum Physics · Physics 2012-02-06 C. H. Fleming , B. L. Hu

We consider a well-known exactly solvable model of an open quantum system with pure decoherence. The aim of this paper is twofold. Firstly, decoherence is a property of open quantum systems important for both quantum technologies and the…

Quantum Physics · Physics 2023-11-28 Anton Trushechkin

A fundamental question in many-body physics is how closed quantum systems reach equilibrium. We address this question experimentally and theoretically in an ultracold large-spin Fermi gas where we find a complex interplay between internal…

We develop an interacting extension of the Double Covariance Model (DCM), a stochastic subquantum framework in which macroscopic quantum dynamics emerge through coarse-graining of correlated microscopic fluctuations. Starting from local…

Quantum Physics · Physics 2026-05-29 Andrei Khrennikov

We investigate a reformulation of the dynamics of interacting fermion systems in terms of a stochastic extension of Time Dependent Hartree-Fock equations. The noise is found from a path-integral representation of the evolution operator and…

Nuclear Theory · Physics 2009-11-07 O. Juillet , Ph. Chomaz , D. Lacroix , F. Gulminelli

Heat transport in open quantum systems is particularly susceptible to the modeling of system-reservoir interactions. It thus requires to consistently treat the coupling between a quantum system and its environment. While perturbative…

Statistical Mechanics · Physics 2017-06-07 Thomas Motz , Joachim Ankerhold , Jürgen T. Stockburger

The time evolution of occupation number is studied for fermionic or bosonic oscillator linearly fully coupled to several fermionic and bosonic heat baths. The influence of characteristics of thermal reservoirs of different statistics on the…

Quantum Physics · Physics 2021-02-12 V. V. Sargsyan , A. A. Hovhannisyan , G. G. Adamian , N. V. Antonenko , D. Lacroix

We consider the problem of decoherence and relaxation of open bosonic quantum systems from a perspective alternative to the standard master equation or quantum trajectories approaches. Our method is based on the dynamics of expectation…

Quantum Physics · Physics 2009-11-13 D. A. R. Dalvit , G. P. Berman , M. Vishik

The exact quantum state evolution of a fermionic gas with binary interactions is obtained as the stochastic average of BCS-state trajectories. We find the most general Ito stochastic equations which reproduce exactly the dynamics of the…

Other Condensed Matter · Physics 2009-02-05 Alberto Montina , Yvan Castin

An approach, called discretized environment method, is introduced to treat exactly non-Markovian effects in open quantum systems. In this approach, a complex environment described by a spectral function is mapped into a finite set of…

Quantum Physics · Physics 2015-06-22 Denis Lacroix , V. V. Sargsyan , G. G. Adamian , N. V. Antonenko

We investigate measures of non-Markovianity in open quantum systems governed by Gaussian free fermionic dynamics. Standard indicators of non-Markovian behavior, such as the BLP and LFS measures, are revisited in this context. We show that…

Quantum Physics · Physics 2025-10-01 Giuliano Chiriacò

We discuss some aspects of a new noncombinatorial fermionic approach to the two-dimensional dimer problem in statistical mechanics based on the integration over anticommuting Grassmann variables and factorization ideas for dimer density…

Statistical Mechanics · Physics 2007-05-23 R. Hayn , V. N. Plechko

Both conservation laws and practical restrictions impose symmetry constraints on the dynamics of open quantum systems. In the case of time-translation symmetry, which arises naturally in many physically relevant scenarios, the quantum…

Quantum Physics · Physics 2017-09-14 Matteo Lostaglio , Kamil Korzekwa , Antony Milne

The control of open quantum systems has a fundamental relevance for fields ranging from quantum information processing to nanotechnology. Typically, the system whose coherent dynamics one wants to manipulate, interacts with an environment…

Mesoscale and Nanoscale Physics · Physics 2007-06-20 Gonzalo A. Alvarez

We outline a non-perturbative approach for simulating the behavior of open quantum systems interacting with a bosonic environment defined by a generalized spectral density function. The method is based on replacing the environment by a set…

Quantum Physics · Physics 2021-08-13 Graeme Pleasance , Francesco Petruccione

We investigate the optimal control problem for non-Markovian open, dissipative quantum system. Optimal control using Pontryagin maximum principle is specifically derived. The influences of Ohmic reservoir with Lorentz-Drude regularization…

Quantum Physics · Physics 2009-10-28 Wei Cui , Zairong Xi , Yu Pan