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The relativistic quantum dynamics of an electrically charged particle subject to the Klein-Gordon oscillator and the Coulomb potential is investigated. By searching for relativistic bound states, a particular quantum effect can be observed:…

Quantum Physics · Physics 2016-05-04 R. L. L. Vitória , C. Furtado , K. Bakke

Quantum contextuality, where measurement outcomes depend on the measurement context, implies a failure of classical realism in quantum systems. As recently shown, the transition between measurement contexts can be mapped onto the path that…

Quantum Physics · Physics 2026-01-22 Yuki Sagawa , Jonte R. Hance , Holger F. Hofmann , Takafumi Ono

We reveal the emergence of environment-induced spontaneous synchronization between two spin-1/2 quantum objects in a collision model setting. In particular, we determine the conditions for the dynamical establishment of synchronous…

Quantum Physics · Physics 2019-08-01 G. Karpat , İ. Yalçınkaya , B. Çakmak

The Dirac equation is solved to obtain its approximate bound states for a spin-1/2 particle in the presence of trigonometric Poschl-Teller (tPT) potential including a Coulomb-like tensor interaction with arbitrary spin-orbit quantum number…

Quantum Physics · Physics 2013-08-02 Babatunde J. Falaye , Sameer M. Ikhdair

The Kochen-Specker theorem theoretically shows evidence of the incompatibility of noncontextual hidden variable theories with quantum mechanics. Quantum contextuality is a more general concept than quantum non-locality which is quite well…

Quantum Physics · Physics 2010-08-05 Yuji Hasegawa , Katharina Durstberger-Rennhofer , Stephan Sponar , Helmut Rauch

The non-classicality of single quantum systems can be formalised using the notion of contextuality. But can contextuality be convincingly demonstrated in an experiment, without reference to the quantum formalism? The operational approach to…

Quantum Physics · Physics 2019-04-19 Matthew F. Pusey , Lídia del Rio , Bettina Meyer

The Klein-Gordon and Dirac equations in a semi-infinite lab ($x > 0$), in the background metric $\ds^2 = u^2(x) (-\dt^2 + \dx^2) + \dy^2 + \dz^2$, are investigated. The resulting equations are studied for the special case $ u(x) = 1 + g x$.…

General Relativity and Quantum Cosmology · Physics 2009-11-07 M. Khorrami , M. Alimohammadi , A. Shariati

We discuss the problem of hidden variables and the motivation for introducting them in quantum mechanics. These include determinism, and the problem of meassurement and incompleteness. We first discuss Von-Neumann's imposisbility proof and…

Quantum Physics · Physics 2007-05-23 Virendra Singh

Effective classicality of a property of a quantum system can be defined using redundancy of its record in the environment. This allows quantum physics to approximate the situation encountered in the classical world: The information about a…

Quantum Physics · Physics 2007-05-23 W. H. Zurek

The problem of the position and spin in relativistic quantum mechanics is analyzed in detail. It is definitively shown that the position and spin operators in the Foldy-Wouthuysen representation (but not in the Dirac one) are…

Quantum Physics · Physics 2020-04-16 Liping Zou , Pengming Zhang , Alexander J. Silenko

We address the propagation of the spin along classical trajectories for a 1/2-spin particle obeying the Dirac equation with scalar potentials. Focusing on classical trajectories as the exact propagation of wave-function discontinuities we…

Quantum Physics · Physics 2014-12-24 Jesús Rubio , Alfredo Luis

Quantum theory departs from classical physics in its treatment of correlations, most prominently through the phenomena of contextuality and nonlocality. Once regarded primarily as foundational curiosities, these effects are now understood…

Quantum Physics · Physics 2026-02-27 Jianqi Sheng , Dongkai Zhang , Lixiang Chen

We study how meaningful physical predictions can arise in nonperturbative quantum gravity in a closed Lorentzian universe. In such settings, recent developments suggest that the quantum gravitational Hilbert space is one-dimensional and…

High Energy Physics - Theory · Physics 2025-06-17 Yasunori Nomura , Tomonori Ugajin

Causality imposes strong restrictions on the type of operators that may be observables in relativistic quantum theories. In fact, causal violations arise when computing conditional probabilities for certain partial causally connected…

Quantum Physics · Physics 2009-11-07 Rodolfo Gambini , Rafael A. Porto

Rotational invariance of physical laws is a generally accepted principle. We show that it leads to an additional external constraint on local realistic models of physical phenomena involving measurements of multiparticle spin 1/2…

Quantum Physics · Physics 2009-11-10 Koji Nagata , Wieslaw Laskowski , Marcin Wiesniak , Marek Zukowski

Quantum measurements are noncontextual, with outcomes independent of which other commuting observables are measured at the same time, when consistently analyzed using principles of Hilbert space quantum mechanics rather than classical…

Quantum Physics · Physics 2013-06-06 Robert B. Griffiths

We study a single quantum particle in discrete spacetime evolving in a causal way. We see that in the continuum limit any massless particle with a two dimensional internal degree of freedom obeys the Weyl equation, provided that we perform…

Quantum Physics · Physics 2014-06-25 Terence C. Farrelly , Anthony J. Short

The Dirac equation for a massive spin-1/2 field in a central potential V in three dimensions is studied without fixing a priori the functional form of V. The second-order equations for the radial parts of the spinor wave function are shown…

High Energy Physics - Theory · Physics 2008-11-26 Giampiero Esposito , Pietro Santorelli

Spin-1/2 particles can be used to study inertial and gravitational effects by means of interferometers, particle accelerators, and ultimately quantum systems. These studies require, in general, knowledge of the Hamiltonian and of the…

General Relativity and Quantum Cosmology · Physics 2007-05-23 D. Singh , G. Papini

Recently, an interesting form of non-classical effect which can be considered as a form of contextuality within quantum mechanics, has been demonstrated for a four-level system by discriminating the different routes that are taken for…

Quantum Physics · Physics 2018-06-05 A. K. Pan , K. Mandal