Generalised Spin Projection for Fermion Actions

Assessing the Calculation of Exchange Coupling Constants and Spin Crossover Gaps Using the Approximate Projection Model to Improve Density Function Calculations

10.26434/chemrxiv.7976474.v2 ◽

2019 ◽

Author(s):

Xianghai Sheng ◽

Lee Thompson ◽

Hrant Hratchian

Keyword(s):

Density Functional Theory ◽

Exchange Coupling ◽

Density Functional ◽

Spin Crossover ◽

Coupling Constants ◽

Spin Projection ◽

Coupling Constant ◽

Projection Model ◽

Functional Theory

This work evaluates the quality of exchange coupling constant and spin crossover gap calculations using density functional theory corrected by the Approximate Projection model. Results show that improvements using the Approximate Projection model range from modest to significant. This study demonstrates that, at least for the class of systems examined here, spin-projection generally improves the quality of density functional theory calculations of J-coupling constants and spin crossover gaps. Furthermore, it is shown that spin-projection can be important for both geometry optimization and energy evaluations. The Approximate Project model provides an affordable and practical approach for effectively correcting spin-contamination errors in molecular exchange coupling constant and spin crossover gap calculations.

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Spin-projection for quantum computation: A low-depth approach to strong correlation

Physical Review Research ◽

10.1103/physrevresearch.2.043142 ◽

2020 ◽

Vol 2 (4) ◽

Author(s):

Takashi Tsuchimochi ◽

Yuto Mori ◽

Seiichiro L. Ten-no

Keyword(s):

Quantum Computation ◽

Strong Correlation ◽

Spin Projection

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Estimation of spin contamination errors in DFT/plane-wave calculations of solid materials using approximate spin projection scheme

Chemical Physics Letters ◽

10.1016/j.cplett.2020.138291 ◽

2021 ◽

Vol 765 ◽

pp. 138291

Author(s):

Kohei Tada ◽

Shusuke Yamanaka ◽

Takashi Kawakami ◽

Yasutaka Kitagawa ◽

Mitsutaka Okumura ◽

...

Keyword(s):

Plane Wave ◽

Spin Projection ◽

Solid Materials ◽

Spin Contamination ◽

Projection Scheme

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Is Einsteinian no-signalling violated in Bell tests?

Open Physics ◽

10.1515/phys-2017-0087 ◽

2017 ◽

Vol 15 (1) ◽

pp. 739-753 ◽

Cited By ~ 6

Author(s):

Marian Kupczynski

Keyword(s):

Quantum Electrodynamics ◽

Probability Distributions ◽

Selection Procedure ◽

Quantum Correlations ◽

Spin Projection ◽

Marginal Probability ◽

Strong Correlations ◽

Relativistic Invariance ◽

Long Range Correlations ◽

Apparent Violation

AbstractRelativistic invariance is a physical law verified in several domains of physics. The impossibility of faster than light influences is not questioned by quantum theory. In quantum electrodynamics, in quantum field theory and in the standard model relativistic invariance is incorporated by construction. Quantum mechanics predicts strong long range correlations between outcomes of spin projection measurements performed in distant laboratories. In spite of these strong correlations marginal probability distributions should not depend on what was measured in the other laboratory what is called shortly: non-signalling. In several experiments, performed to test various Bell-type inequalities, some unexplained dependence of empirical marginal probability distributions on distant settings was observed. In this paper we demonstrate how a particular identification and selection procedure of paired distant outcomes is the most probable cause for this apparent violation of no-signalling principle. Thus this unexpected setting dependence does not prove the existence of superluminal influences and Einsteinian no-signalling principle has to be tested differently in dedicated experiments. We propose a detailed protocol telling how such experiments should be designed in order to be conclusive. We also explain how magical quantum correlations may be explained in a locally causal way.

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