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Related papers: Multiconfigurational quantum chemistry: The CASPT2…

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We show that by working in a basis similar to that of the natural transition orbitals and using a modified zeroth order Hamiltonian, the cost of a recently-introduced perturbative correction to excited state mean field theory can be reduced…

Chemical Physics · Physics 2020-09-03 Rachel Clune , Jacqueline A. R. Shea , Eric Neuscamman

The Schr\"odinger functional (SF) is a powerful and widely used tool for the treatment of a variety of problems in renormalization and related areas. Albeit offering many conceptual advantages, one major downside of the SF scheme is the…

High Energy Physics - Lattice · Physics 2013-11-06 Michele Brambilla , Mattia Dalla Brida , Francesco Di Renzo , Dirk Hesse , Stefan Sint

A geometric approach to general quantum statistical systems (including the harmonic oscillator) is presented. It is applied to Casimir energy and the dissipative system with friction. We regard the (N+1)-dimensional Euclidean {\it…

High Energy Physics - Theory · Physics 2011-01-28 Shoichi Ichinose

We report an efficient implementation of a second-order multireference perturbation theory based on the driven similarity renormalization group (DSRG-MRPT2) [C. Li and F. A. Evangelista, J. Chem. Theory Comput. 11, 2097 (2015)]. Our…

Chemical Physics · Physics 2016-06-22 Kevin P. Hannon , Chenyang Li , Francesco A. Evangelista

Quantum coherence profoundly alters classical thermodynamic expectations by modifying the structure and accessibility of probability distributions. Classically, transitions to lower-entropy states (local second-law violations) are…

Quantum Physics · Physics 2025-05-20 Andrei Tudor Patrascu

We present a new characterization of quantum theory in terms of simple physical principles that is different from previous ones in two important respects: first, it only refers to properties of single systems without any assumptions on the…

Quantum Physics · Physics 2015-01-06 Howard Barnum , Markus P. Mueller , Cozmin Ududec

Time-dependent response theories are foundational to the development of algorithms that determine quantum properties of electronic excited states of molecules and periodic systems. They are employed in wave-function, density-functional, and…

Chemical Physics · Physics 2022-11-23 Martín A. Mosquera

Excited states play a central role in determining the physical properties of quantum matter, yet their accurate computation in many-body systems remains a formidable challenge for numerical methods. While neural quantum states have…

Quantum Physics · Physics 2025-07-15 Douglas Hendry , Alessandro Sinibaldi , Giuseppe Carleo

The role of multi-parameter entanglement in quantum interference from collinear type-II spontaneous parametric down-conversion is explored using a variety of aperture shapes and sizes, in regimes of both ultrafast and continuous-wave…

We develop a quantum computing scheme utilizing McLachlan variational principle in a hybrid quantum-classical algorithm to accurately calculate the transition dynamics of a closed quantum system with many excited states subject to a strong…

Quantum Physics · Physics 2022-04-26 Yulun Wang , Predrag S. Krstic

The multi-reference Coupled Cluster method first proposed by Meller et al (J. Chem. Phys. 1996) has been implemented and tested. Guess values of the amplitudes of the single and double excitations (the ${\hat T}$ operator) on the top of the…

Chemical Physics · Physics 2016-04-11 Emmanuel Giner , Grégoire David , Anthony Scemama , Jean Paul Malrieu

UGA-SSMRPT2, the spin-free perturbative analogue of Mukerjee's State-Specific Multireference Coupled Cluster Theory (MkMRCC) is known to be successful for size-extensive and intruder-free construction of dissociation curves. This work…

Chemical Physics · Physics 2026-02-05 Shamik Chanda , Pratyush Bhattacharjya , Avijit Sen , Sangita Sen

It is a universal phenomenon that the state and input of the continuous stirred tank reactor (CSTR) systems are both disturbed. This paper proposes a (state, input)-disturbed port-Hamiltonian framework that can be used to model and further…

Optimization and Control · Mathematics 2017-07-07 Yafei Lu , Zhou Fang , Chuanhou Gao

Quantum computation for chemical problems will require the construction of guiding states with sufficient overlap with a target state. Since easily available and initializable mean-field states are characterized by an overlap that is…

Computational Physics · Physics 2024-09-16 Maximilian Mörchen , Guang Hao Low , Thomas Weymuth , Hongbin Liu , Matthias Troyer , Markus Reiher

Despite significant work on resource estimation for quantum simulation of electronic systems, the challenge of preparing states with sufficient ground state support has so far been largely neglected. In this work we investigate this issue…

We consider the behaviour of a critical system in the presence of a gradient perturbation of the couplings. In the direction of the gradient an interface region separates the ordered phase from the disordered one. We develop a scaling…

Other Condensed Matter · Physics 2009-10-06 Thierry Platini , Dragi Karevski , Loïc Turban

A strategy for finding transition paths connecting two stable basins is presented. The starting point is the Hamilton principle of stationary action; we show how it can be transformed into a minimum principle through the addition of…

Materials Science · Physics 2009-11-07 Daniele Passerone , Matteo Ceccarelli , Michele Parrinello

Downfolding coupled cluster (CC) techniques have recently been introduced into quantum chemistry as a tool for the dimensionality reduction of the many-body quantum problem. As opposed to earlier formulations in physics and chemistry based…

Quantum Physics · Physics 2022-03-23 Nicholas P. Bauman , Karol Kowalski

This note is a comment on the "quantum interferometry" section of Reference [1]. It points out that the methods of that section can be applied to more general states than the ones that are discussed in Ref. [1].

Quantum Physics · Physics 2007-05-23 Filippo Neri

The multiconfigurational time-dependent Hartree method (MCTDH) [Chem. Phys. Lett. {\bf 165}, 73 (1990); J. Chem. Phys. {\bf 97}, 3199 (1992)] is celebrating nowadays entering its third decade of tackling numerically-exactly a broad range of…

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