Downloads & Free Reading Options - Results

The nature of time, mass, and spacetime geometry continues to be a central question in modern physics. While General Relativity (GR) and Quantum Field Theory (QFT) have proven remarkably successful within their respective domains, they remain fundamentally incompatible at their foundations. GR treats spacetime as a continuous geometric manifold, shaped by the presence of mass and energy, whereas QFT describes particles and fields as excitations over a fixed background spacetime, with quantum coherence playing no explicit geometric role. In recent decades, the concept of emergent spacetime has gained attention as a potential route to reconciling these paradigms. Concurrently, advances in quantum information theory have provided new tools to describe the structure and dynamics of quantum systems in terms of information-theoretic measures such as coherence, entropy, and entanglement. This has led to the proposal that spacetime geometry itself may be a manifestation of deeper informational structures. This paper introduces and formalizes a new theoretical model, where in time, mass, and geometry emerge from the underlying dynamics of quantum coherence.

The total correlations in a bipartite quantum system are measured by the quantum mutual information $\mathcal{I}$, which consists of quantum discord and classical correlation. However, recent results in quantum information shows that coherence, which is a part of total correlation, is more general and more fundamental than discord. The role of coherence in quantum resource theories is worthwhile to investigate. We first study the relation between quantum discord and coherence by reducing the difference between them. And then, we consider the dynamics of quantum discord, classical correlations and quantum coherence under incoherent quantum channels. We discover that coherence indicate the behavior of quantum discord (classical correlation) for times $t \bar t$. What is more, the coherence frozen and decay indicate the quantum discord and classical correlation frozen and decay respectively.

Coupled quantum dots are an example of the ubiquitous quantum double potential well. In a typical transport experiment, each quantum dot is also coupled to a continuum of states. Our approach takes this into account by using a Green's function formalism to solve the full system. The time-dependent solution is then explored in different limiting cases. In general, a combination of coherent and incoherent behavior is observed. In the case that the coupling of each dot to the macroscopic world is equal, however, the time evolution is purely coherent.

In Crull (2015) it is argued that, in order to confront outstanding problems in cosmology and quantum gravity, interpretational aspects of quantum theory can by bypassed because decoherence is able to resolve them. As a result, Crull (2015) concludes that our focus on conceptual and interpretational issues, while dealing with such matters in Okon and Sudarsky (2014), is avoidable and even pernicious. Here we will defend our position by showing in detail why decoherence does not help in the resolution of foundational questions in quantum mechanics, such as the measurement problem or the emergence of classicality.

We consider surface diffusion of a single particle, which performs site-to-site under-barrier hopping, fulfils intrasite motion between the ground and the first excited states within a quantum well, and interacts with surface phonons. On the basis of quantum kinetic equations for one-particle distribution functions obtained earlier we study the coherent and incoherent motion of the adparticle. In the latter case we derive the generalized diffusion coefficients and study various dynamic regimes of the adparticle. The critical values of the coupling constant $G_{cr}(T,\Omega)$, which separate domains with possible recrossing from those with the monotonic motion of the adparticle, are calculated as functions of a temperature $T$ and a vibrational frequency $\Omega$. These domains are found to coincide with the regions where the experimentally observed diffusion coefficients change its behavior from weakly dependent on $T$ to quite a sensitive function of the temperature. We also evaluate the off-diagonal (relative to the site labels) distribution functions both in the Markovian limit and when the memory effects become important. The obtained results are discussed in the context of the "long tails" problem of the generalized diffusion coefficients, the recrossing/multiple crossing phenomena, and an eventual interrelation between the adparticle dynamics at short times and the temperature dependence of the diffusion coefficients measured experimentally.

The prospect of developing magnetic qubits is discussed. The first part of the article makes suggestions on how to achieve the coherent quantum superposition of spin states in small ferromagnetic clusters, weakly uncompensated antiferromagnetic clusters, and magnetic molecules. The second part of the article deals with mechanisms of decoherence expected in magnetic systems. Main decohering effects are coming from nuclear spins and magnetic fields. They can be reduced by isotopic purification and superconducting shielding. In that case the time reversal symmetry of spin Hamiltonians makes spin-phonon coupling ineffective in destroying quantum coherence.