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The existence of the delocalized-localized quantum phase transition (QPT) in the ohmic spin-boson model has been commonly recognized. While the physics in the localized regime is relatively simple, the delocalized regime shows many…

Quantum Physics · Physics 2011-11-15 Qing-Jun Tong , Jun-Hong An , Hong-Gang Luo , C. H. Oh

We derive an extension of the quantum regression theorem to calculate out-of-time-order correlation functions in Markovian open quantum systems. While so far mostly being applied in the analysis of many-body physics, we demonstrate that…

Quantum Physics · Physics 2019-03-13 Philip Daniel Blocher , Klaus Molmer

We analytically derive the exact -- though formal -- master equation for a two-level quantum system (qubit) interacting with a bosonic environment within the rotating-wave approximation, assuming the environment is initially in an arbitrary…

Quantum Physics · Physics 2025-10-16 Hiromichi Nakazato , Saverio Pascazio

We develop a perturbation theory of quantum (and classical) master equations with slowly varying parameters, applicable to systems which are externally controlled on a time scale much longer than their characteristic relaxation time. We…

Quantum Physics · Physics 2017-08-09 Vasco Cavina , Andrea Mari , Vittorio Giovannetti

We present a quantum averaging theory (QAT) for analytically modeling unitary gate dynamics in driven quantum systems beyond the rotating-wave approximation. QAT addresses the simultaneous presence of distinct timescales by generating a…

Quantum Physics · Physics 2026-01-05 Kristian D. Barajas , Wesley C. Campbell

Quantum many body system in equilibrium can be effectively characterized using the framework of quantum statistical mechanics. However, nonequilibrium behaviour of quantum many body systems remains elusive, out of the range of such a well…

Quantum Physics · Physics 2020-05-14 Bing Chen , Xianfei Hou , Feifei Zhou , Peng Qian , Heng Shen , Nanyang Xu

In this paper, we address the challenge of multivariate time-series forecasting using quantum machine learning techniques. We introduce adaptation strategies that extend variational quantum circuit models, traditionally limited to…

The coupling of a qubit to a macroscopic reservoir plays a fundamental role in understanding the complex transition from the quantum to the classical world. Considering a harmonic environment, we use both intuitive arguments and numerical…

Mesoscale and Nanoscale Physics · Physics 2013-02-01 Soumya Bera , Serge Florens , Harold Baranger , Nicolas Roch , Ahsan Nazir , Alex Chin

In the Quantum-Train (QT) framework, mapping quantum state measurements to classical neural network weights is a critical challenge that affects the scalability and efficiency of hybrid quantum-classical models. The traditional QT framework…

Quantum Physics · Physics 2024-09-12 Chen-Yu Liu , Chu-Hsuan Abraham Lin , Kuan-Cheng Chen

In this paper, we present a comprehensive account of quantum dissipation theories with the quadratic environment couplings. The theoretical development includes the Brownian solvation mode embedded hierarchical quantum master equations, a…

Quantum Physics · Physics 2023-02-07 Zi-Hao Chen , Yao Wang , Rui-Xue Xu , YiJing Yan

Covariant codes are quantum codes such that a symmetry transformation on the logical system could be realized by a symmetry transformation on the physical system, usually with limited capability of performing quantum error correction (an…

Quantum Physics · Physics 2021-08-11 Sisi Zhou , Zi-Wen Liu , Liang Jiang

We develop an extension of the process matrix (PM) framework for correlations between quantum operations with no causal order that allows multiple rounds of information exchange for each party compatibly with the assumption of well-defined…

Quantum Physics · Physics 2021-01-27 Timothée Hoffreumon , Ognyan Oreshkov

We introduce the concept of quantum observables over time (QOOT), an operator that jointly describes two observables at two distinct time points, as a dual of the quantum state over time formalism. We provide a full characterization of the…

Quantum Physics · Physics 2024-12-17 Gabriele Bressanini , Farhan Hanif , Hyukjoon Kwon , M. S. Kim

Quantile Regression (QR) can be used to estimate aleatoric uncertainty in deep neural networks and can generate prediction intervals. Quantifying uncertainty is particularly important in critical applications such as clinical diagnosis,…

Machine Learning · Computer Science 2023-09-15 Haleh Akrami , Omar Zamzam , Anand Joshi , Sergul Aydore , Richard Leahy

Accurate temperature estimation in the quantum and cryogenic regimes remains a fundamental challenge. Here, we investigate nonequilibrium quantum thermometry using a single-qubit probe coupled to a bosonic bath through noncommuting…

Quantum Physics · Physics 2025-12-23 Youssef Aiache , Abderrahim El Allati , İlkay Demir , Khadija El Anouz

We solve the dynamics of an ensemble of interacting rotors coupled to two leads at different chemical potential letting a current flow through the system and driving it out of equilibrium. We show that at low temperature the coarsening…

Disordered Systems and Neural Networks · Physics 2015-03-17 Camille Aron , Giulio Biroli , Leticia F. Cugliandolo

Quantum reservoir computing (QRC) leverages the high-dimensional, nonlinear dynamics inherent in quantum many-body systems for extracting spatiotemporal patterns in sequential and time-series data with minimal training overhead. Although…

Quantum Physics · Physics 2025-10-22 Shehbaz Tariq , Muhammad Talha , Symeon Chatzinotas , Hyundong Shin

We introduces the Quantum-Train(QT) framework, a novel approach that integrates quantum computing with classical machine learning algorithms to address significant challenges in data encoding, model compression, and inference hardware…

Complete information on the equilibrium behaviour and dynamics of a quantum field theory (QFT) is provided by multipoint correlation functions. However, their theoretical calculation is a challenging problem, even for exactly solvable…

Statistical Mechanics · Physics 2018-09-19 Ivan Kukuljan , Spyros Sotiriadis , Gabor Takacs

We consider thermal machines powered by locally equilibrium reservoirs that share classical or quantum correlations. The reservoirs are modelled by the so-called collisional model or repeated interactions model. In our framework, two…

Quantum Physics · Physics 2020-08-28 Gabriele De Chiara , Mauro Antezza