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Quantum and classical systems can consistently be coupled via non-unitary time-irreversible mechanisms. In this paper we characterize which kind of corresponding dynamics converge in the stationary regime to a thermal hybrid state, that is,…

Quantum Physics · Physics 2026-04-06 Adrián A. Budini

Parity-time ($PT$) symmetric Hamiltonians are generally non-Hermitian and give rise to exotic behaviour in quantum systems at exceptional points, where eigenvectors coalesce. The recent realisation of $PT$-symmetric Hamiltonians in quantum…

The development of non-Hermitian topological band theory has led to observations of novel topological phenomena in effectively classical, driven and dissipative systems. However, for open quantum many-body systems, the absence of a ground…

Mesoscale and Nanoscale Physics · Physics 2021-07-14 Sharareh Sayyad , Jinlong Yu , Adolfo G. Grushin , Lukas M. Sieberer

Quantum many-body systems are characterized by their correlations. While equal-time correlators and unequal-time commutators between operators are standard observables, the direct access to unequal-time anti-commutators poses a formidable…

Quantum Gases · Physics 2022-09-30 Kevin T. Geier , Philipp Hauke

The eigenstate thermalization hypothesis (ETH) has been highly influential in explaining thermodynamic behavior of closed quantum systems. As of yet, it is unclear whether and how the ETH applies to non-Hermitian systems. Here, we introduce…

Unitary and dissipative models of quantum dynamics are linear maps on the space of states or density matrices. This linearity encodes the superposition principle, a key feature of quantum theory. However, this principle can break down in…

Quantum Physics · Physics 2025-10-31 Orion Lee , Qian Cao , Yogesh N. Joglekar , Kater Murch

Recent experimental advancements in dissipation control have yielded significant insights into non-hermitian Hamiltonians for open quantum systems. Of particular interest are the topological characteristics exhibited by these non-hermitian…

Mesoscale and Nanoscale Physics · Physics 2025-11-06 David Christian Ohnmacht , Valentin Wilhelm , Hannes Weisbrich , Wolfgang Belzig

The prominent collective character of long-range interacting quantum systems makes them promising candidates for quantum technological applications. Yet, lack of additivity overthrows the traditional picture for entanglement scaling and…

Quantum Physics · Physics 2023-08-07 Guido Giachetti , Nicolo Defenu

Understanding the dynamics of dissipative quantum systems, particularly beyond the weak coupling approximation, is central to various quantum applications. While numerically exact methods provide accurate solutions, they often lack the…

Quantum Physics · Physics 2024-06-26 Marlon Brenes , Brett Min , Nicholas Anto-Sztrikacs , Nir Bar-Gill , Dvira Segal

We investigate the finite time thermodynamics of a single-level fermion system interacting with a thermal reservoir through a tunneling junction. The optimal protocol to extract the maximum work from the system when moving the single energy…

Statistical Mechanics · Physics 2015-05-14 Massimiliano Esposito , Ryoichi Kawai , Katja Lindenberg , Christian Van den Broeck

The Eigenstate Thermalization Hypothesis (ETH) represents a cornerstone in the theoretical understanding of the emergence of thermal behavior in closed quantum systems. The ETH asserts that expectation values of simple observables in energy…

Statistical Mechanics · Physics 2024-05-15 Giorgio Cipolloni , Jonah Kudler-Flam

Dissipation in open systems enriches the possible symmetries of the Hamiltonians beyond the Hermitian framework allowing the possibility of novel non-Hermitian topological phases, which exhibit long-living end states that are protected…

Quantum Physics · Physics 2023-04-05 Wojciech Brzezicki , Matti Silveri , Marcin Płodzień , Francesco Massel , Timo Hyart

We study exceptional points (EPs) of a nonhermitian Hamiltonian $\hat{H}(\lambda,\delta)$ whose parameters $\lambda \in {\mathbb C}$ and $\delta \in {\mathbb R}$. As the real control parameter $\delta$ is varied, the $k$-th EP (or $k$-th…

Quantum Physics · Physics 2023-03-22 Milan Šindelka , Pavel Stránský , Pavel Cejnar

We design several examples of constrained, symmetric quantum circuit dynamics that generate non-equilibrium steady states. The qubit networks maintain local memory of the initial conditions and display inhomogeneous subsystem dynamics over…

Quantum Physics · Physics 2025-05-02 Unnati Akhouri , Sarah Shandera , Jackson Henry

Complex spectra of dissipative quantum systems may exhibit degeneracies known as exceptional points (EPs). At these points the systems' dynamics may undergo drastic changes. Phenomena associated with EPs and their applications have been…

Quantum Physics · Physics 2025-03-19 Andrei I. Pavlov , Yuval Gefen , Alexander Shnirman

The physics of systems that cannot be described by a Hermitian Hamiltonian, has been attracting a great deal of attention in recent years, motivated by their nontrivial responses and by a plethora of applications for sensing, lasing, energy…

Optics · Physics 2021-03-16 Alex Krasnok , Nikita Nefedkin , Andrea Alu

It is expected that a generic closed many-body system prepared in a well-behaved initial state and subjected to a periodic drive will eventually thermalize, i.e. approach the state of maximal entropy. This property, while compatible with…

Statistical Mechanics · Physics 2026-03-17 Anton Kapustin

We discuss in general how to geometrically visualize a qudit system, with a particular interest in thermal states. The principle of maximum entropy is used to study the geometric properties of an ensemble of finite dimensional Hamiltonian…

Quantum Physics · Physics 2025-02-10 J. A. López-Saldívar , O. Castaños , S. Cordero , E. Nahmad-Achar , R. López-Peña

The periodically modulated Bose-Hubbard dimer model offers an experimentally realizable and highly tunable platform for observing the scrambling of quantum information and the apparent thermalisation of isolated, interacting quantum…

Quantum Physics · Physics 2020-09-02 Ryan A. Kidd , Arghavan Safavi-Naini , Joel F. Corney

Ultracold atomic physics experiments offer a nearly ideal context for the investigation of quantum systems far from equilibrium. We describe three related emerging directions of research into extreme non-equilibrium phenomena in atom traps:…