Search results for " graph"
showing 10 items of 1277 documents
Generalized Interaction-Free Evolutions
2015
A thorough analysis of the evolutions of bipartite systems characterized by the \lq effective absence\rq\, of interaction between the two subsystems is reported. First, the connection between the concepts underlying Interaction-Free Evolutions (IFE) and Decoherence-Free Subspaces (DFS) is explored, showing intricate relations between these concepts. Second, starting from this analysis and inspired by a generalization of DFS already known in the literature, we introduce the notion of generalized IFE (GIFE), also providing a useful characterization that allows to develop a general scheme for finding GIFE states.
Class of exact memory-kernel master equations
2016
A well-known situation in which a non-Markovian dynamics of an open quantum system $S$ arises is when this is coherently coupled to an auxiliary system $M$ in contact with a Markovian bath. In such cases, while the joint dynamics of $S$-$M$ is Markovian and obeys a standard (bipartite) Lindblad-type master equation (ME), this is in general not true for the reduced dynamics of $S$. Furthermore, there are several instances (\eg the dissipative Jaynes-Cummings model) in which a {\it closed} ME for the $S$'s state {\it cannot} even be worked out. Here, we find a class of bipartite Lindblad-type MEs such that the reduced ME of $S$ can be derived exactly and in a closed form for any initial produ…
Interaction free and decoherence free states
2015
An interaction free evolving state of a closed bipartite system composed of two interacting subsystems is a generally mixed state evolving as if the interaction were a c-number. In this paper we find the characteristic equation of states possessing similar properties for a bipartite systems governed by a linear dynamical equation whose generator is sum of a free term and an interaction term. In particular in the case of a small system coupled to its environment, we deduce the characteristic equation of decoherence free states namely mixed states evolving as if the interaction term were effectively inactive. Several examples illustrate the applicability of our theory in different physical co…
Bilayer graphene lattice-layer entanglement in the presence of non-Markovian phase noise
2018
The evolution of single particle excitations of bilayer graphene under effects of non-Markovian noise is described with focus on the decoherence process of lattice-layer (LL) maximally entangled states. Once that the noiseless dynamics of an arbitrary initial state is identified by the correspondence between the tight-binding Hamiltonian for the AB-stacked bilayer graphene and the Dirac equation -- which includes pseudovector- and tensor-like field interactions -- the noisy environment is described as random fluctuations on bias voltage and mass terms. The inclusion of noisy dynamics reproduces the Ornstein-Uhlenbeck processes: a non-Markovian noise model with a well-defined Markovian limit…
Stochastic collision model approach to transport phenomena in quantum networks
2021
Abstract Noise-assisted transport phenomena highlight the nontrivial interplay between environmental effects and quantum coherence in achieving maximal efficiency. Due to the complexity of biochemical systems and their environments, effective open quantum system models capable of providing physical insights on the presence and role of quantum effects are highly needed. In this paper, we introduce a new approach that combines an effective quantum microscopic description with a classical stochastic one. Our stochastic collision model (SCM) describes both Markovian and non-Markovian dynamics without relying on the weak coupling assumption. We investigate the consequences of spatial and tempora…
On heavy baryon decay form factors
1991
We consider in detail the consequences of the heavy quark mass limit in the weak decay of 1/2+ heavy baryons to 1/2+ and 3/2+ heavy baryon final states. We also analyze heavy baryon to light baryon transitions as well ase+e−-annihilation into heavy baryon-antibaryonpairs. We discuss possible approximations to the most general approach and some of their implications for future experiments.
Constraints on Area Variables in Regge Calculus
2000
We describe a general method of obtaining the constraints between area variables in one approach to area Regge calculus, and illustrate it with a simple example. The simplicial complex is the simplest tessellation of the 4-sphere. The number of independent constraints on the variations of the triangle areas is shown to equal the difference between the numbers of triangles and edges, and a general method of choosing independent constraints is described. The constraints chosen by using our method are shown to imply the Regge equations of motion in our example.
Robust Two-Dimensional Electronic Properties in Three-Dimensional Microstructures of Rotationally Stacked Turbostratic Graphene
2017
We report on the electronic properties of turbostratic graphitic microdisks, rotationally stacked systems of graphene layers, where interlayer twisting leads to electronic decoupling resulting in charge-transport properties that retain the two dimensionality of graphene, despite the presence of a large number of layers. A key fingerprint of this reduced dimensionality is the effect of weak charge-carrier localization that we observe at low temperatures. The disks' resistivity measured as a function of magnetic field changes its shape from parabolic at room temperature to linear at a temperature of 2.7 K indicating further this type of two-dimensional transport. Compared to Bernal stacked gr…
Universal extra dimensions andZ→bb¯
2003
We study, at the one loop level, the dominant contributions from a single universal extra dimension to the process $\stackrel{\ensuremath{\rightarrow}}{Z}b\overline{b}.$ By resorting to the gaugeless limit of the theory we explain why the result is expected to display a strong dependence on the mass of the top quark, not identified in the early literature. A detailed calculation corroborates this expectation, giving rise to a lower bound for the compactification scale which is comparable to that obtained from the $\ensuremath{\rho}$ parameter. An estimate of the subleading corrections is furnished, together with a qualitative discussion on the difference between the present results and thos…
Online Data Reduction using Track and Vertex Reconstruction on GPUs for the Mu3e Experiment
2017
The Mu3e experiment searches for the lepton flavour violating decay μ + → e + e − e + , aiming to achieve a sensitivity of 2 · 10 −15 in its first phase and ultimately aspiring to a final sensitivity of 10 −16 . During the first phase of the experiment, a muon rate of ∼ 10 8 μ /s will be available, resulting in a data rate of ∼ 80 Gbit/s. The trigger-less readout system is based on optical links and switching FPGAs sending the complete detector data for a time slice to one node of the filter farm. A full online reconstruction is necessary to reduce the data rate to a manageable amount to be written to disk. Graphics processing units (GPUs) are used to fit tracks with a non-iterative 3D trac…