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We study dynamical correlations of two coupled large spins depending on the time and on the spin quantum numbers. In the high-temperature approximation, we obtain analytical expressions for the mutual informations, quantum and classical…

Quantum Physics · Physics 2015-06-12 V. E. Zobov

Quantum fluctuations or other moments of a state contribute to energy expectation values and can imply interesting physical effects. In quantum cosmology, they turn out to be important for a discussion of density bounds and instabilities of…

General Relativity and Quantum Cosmology · Physics 2014-07-02 Martin Bojowald

There is a renewed interest in the derivation of statistical mechanics from the dynamics of closed quantum systems. A central part of this program is to understand how far-from-equilibrium closed quantum system can behave as if relaxing to…

In quantum mechanics, it is often thought that the spin of an object points in a fixed direction at any point in time. For example, after selecting the z-direction as the axis of quantization, a spin-1/2 object (such as an electron) may…

Quantum Physics · Physics 2020-01-16 Stuart Samuel

In this work, we investigate the consequences of Lorentz-violating terms in the thermodynamic properties of a 1-dimensional quantum ring. Particularly, we use the ensemble theory to obtain our results of interest. The thermodynamic…

Quantum Physics · Physics 2024-06-10 A. A. Araújo Filho , H. Hassanabadi , J. A. A. S. Reis , L. Lisboa-Santos

We study theoretically the properties of two Bose-Einstein condensates in different spin states, represented by a double Fock state. Individual measurements of the spins of the particles are performed in transverse directions, giving access…

Quantum Physics · Physics 2009-11-13 Franck Laloë , William J. Mullin

Heat spontaneously flows from hot to cold in standard thermodynamics. However, the latter theory presupposes the absence of initial correlations between interacting systems. We here experimentally demonstrate the reversal of heat flow for…

Using a very simple Gedankenexperiment, I remind the reader that (contrary to what happens in classical mechanics) the energy of a quantum system is inevitably increased just by performing (some) textbook measurements on it. As a direct…

Quantum Physics · Physics 2014-02-14 Pablo Echenique-Robba

Aspects of quantum mechanics on a ring are studied. Either one or two impenetrable barriers are inserted at nodal and non-nodal points to turn the ring into either one or two infinite square wells. In the process, the wave function of a…

Quantum Physics · Physics 2016-05-24 Bernhard K. Meister

Many theoretical expressions of dissipation along non-equilibrium processes have been proposed. However, they have not been fully verified by experiments. Especially for systems strongly interacting with environments the connection between…

Statistical Mechanics · Physics 2019-12-03 Ketan Goyal , Xian He , Ryoichi Kawai

We study numerically the process of nuclear spin measurement in a solid-state quantum computer of the type proposed by Kane by modeling the quantum dynamics of two coupled nuclear spins on $^{31}$P donors implanted in silicon. We estimate…

Condensed Matter · Physics 2007-05-23 Gennady P. Berman , David K. Campbell , Gary D. Doolen , Kirill E. Nagaev

We establish the foundations of a nonequilibrium theory of quantum thermodynamics for noninteracting open quantum systems strongly coupled to their reservoirs within the framework of the nonequilibrium Green functions (NEGF). The energy of…

Statistical Mechanics · Physics 2015-03-18 Massimiliano Esposito , Maicol A. Ochoa , Michael Galperin

Recently, three experiments have been proposed in order to show that the standard and Bohmian quantum mechanics can have different predictions at the individual level of particles. However, these thought experiments have encountered some…

Quantum Physics · Physics 2007-05-23 M. Golshani , O. Akhavan

In this paper we introduce a simple procedure for computing the macroscopic quantum behaviour of periodic quantum systems in the high energy regime. The macroscopic quantum coherence is ascribed to a one-particle state, not to a condensate…

Quantum Physics · Physics 2015-06-17 A. Martín-Ruiz , J. Bernal , Adrián Carbajal-Domínguez

This note starts with a recapitulation of what people call the ``Measurement Problem'' of Quantum Mechanics (QM). The dissipative nature of the quantum-mechanical time-evolution of averages of states over large ensembles of identical…

Quantum Physics · Physics 2026-03-27 Jürg Fröhlich , Alessandro Pizzo

Following on from our recent work, we investigate a stochastic approach to non-equilibrium quantum spin systems. We show how the method can be applied to a variety of physical observables and for different initial conditions. We provide…

Statistical Mechanics · Physics 2020-01-24 S. De Nicola , B. Doyon , M. J. Bhaseen

We consider a double quantum dot system with two embedded and non-aligned spin impurities to manipulate the magnitude and polarization of the electron spin density. The device is attached to semi-infinite one-dimensional leads which are…

Mesoscale and Nanoscale Physics · Physics 2009-11-13 Gianluca Stefanucci , Enrico Perfetto , Michele Cini

One of the most surprising consequences of quantum mechanics is the entanglement of two or more distant particles. In an entangled EPR two-particle system, the value of the momentum (position) for neither single subsystem is determined.…

Quantum Physics · Physics 2007-06-18 Yanhua Shih

A brief review is given of the physical implementation of quantum computation within spin systems or other two-state quantum systems. The importance of the controlled-NOT or quantum XOR gate as the fundamental primitive operation of quantum…

Mesoscale and Nanoscale Physics · Physics 2009-10-28 David P. DiVincenzo

We propose a solid state based protocol to implement the universal quantum storage for electronic spin qubit. The quantum memory in this scheme is the spin wave excitation in the ring array of nuclei in a quantum dot. We show that the…

Quantum Physics · Physics 2007-05-23 Y. D. Wang , Y. Li , Z. Song , C. P. Sun