The generalization of the geometric phase to realm mixed states is known as Uhlmann phase. Recently, applications this concept field topological insulators have been made and an experimental observation a characteristic critical temperature at which disappears has also reported. Surprisingly, our knowledge, such paradigmatic system spin-$j$ particle in presence slowly rotating magnetic not reported date. Here we study case thermal ensemble. We find that given by argument complex valued...

To sensitively test scaling in the two-dimensional $\mathrm{XY}$ model quenched from high temperatures into ordered phase, we study difference between measured correlations and (scaling) results of a Gaussian-closure approximation. We also directly compare various length scales. All our are consistent with dynamical an asymptotic growth law $L\ensuremath{\sim}(t/\mathrm{ln}[{t/t}_{0}]{)}^{1/2}$, though time scale ${t}_{0}$ that depends on question. then reconstruct minimal-energy...

We show that the tunable hybridization between two lateral quantum dots connected to a nonmagnetic current leads in “hanging-dot” configuration can be used implement bipolar spin filter. The competition Zeeman, exchange interaction, and interdot tunneling (molecular hybridization) yields singlet-triplet transition of double dot ground state allows filtering Coulomb blockade experiments. Its generic nature should make it broadly useful as robust bidirectional polarizer.

The exchange coupling between two spins has been proposed as a control parameter over the states of two-qubit space, so that it can be used to produce quantum gate operations, and in particular, ${(\text{SWAP})}^{\ensuremath{\alpha}}$ gate. In this work, we study effect Dzyaloshinski-Moriya term (DM) on operation. By considering time-dependent interaction have calculated dynamical properties for probability spin states, magnetization, concurrence, fidelity required determine anisotropic We...

We study the role of dissipation and structural defects on time evolution quantum dot arrays with mobile charges under external driving fields. These structures, proposed as cellular automata, exhibit interesting dynamics which we describe in terms equations motion for density matrix. Using an open system approach, asymmetries microscopic electron-phonon interaction general dynamical behavior charge distribution (polarization) such systems. find that response to field is improved at low...

We study the geometric Uhlmann phase of mixed states at finite temperature in a system two coupled spin-$\frac{1}{2}$ particles driven by magnetic field applied to one spins. In parameter space and coupling, we show emergence topological transitions when evolves around equator, where winding number can characterize each range. For small couplings, width gap nontrivial is roughly critical ${T}_{c}$ one-dimensional fermion systems with two-band Hamiltonians. The first transition...

The zero-temperature ordering kinetics of conserved XY models in spatial dimensions d=2 and 3 is studied using cell dynamical simulations. growth the characteristic length scale L(t) fully consistent with recent theoretical predictions: L(t)\ensuremath{\sim}${\mathit{t}}^{1/4}$ for L(t)\ensuremath{\sim}(t lnt${)}^{1/4}$ d=3. A Gaussian closure approximation describes form structure factor rather well

We study the geometric Uhlmann phase of entangled mixed states in a composite system made two coupled spin-$\frac{1}{2}$ particles with magnetic field acting on one them. Within uniform noisy quantum channel setup, an exact analytical expression for this each subsystem is derived. find explicit connection to concurrence density matrix such channel, which allows us characterize features terms degree entanglement system. In space direction and coupling parameter, it exhibits singularity...

We study the ${H}^{3\ifmmode\times\else\texttimes\fi{}N}$ hybrid entanglement between charge and vibrational modes in a triple-quantum-dot shuttle system. Three quantum dots are linearly connected, with outer fixed central dot oscillating, described as harmonic oscillator oscillation that entangled electronic states of dots. The characterized by Schmidt number function parameters system: detuning inverse tunneling length. show at steady state, detuning, excited lower energy present Bell-type...

Bloch oscillations arise when electrons are in a one-dimensional linear chain of atoms under constant electric field. In this paper we show numerically that different types carbon nanotubes with frequency proportional to the field applied along nanotube axis. We these oscillations, calculating quadratic displacement as function Because double periodicity nanotubes' geometry (the lattice and lines atoms) two frequencies appear, one twice value other. These coincide perfectly those predicted...

We study the dynamic scaling properties of systems with a conserved order parameter O(n) symmetry, using Gaussian auxiliary field approach Mazenko [Phys. Rev. Lett. 63, 1605 (1989); Phys. B 42, 4487 (1990); 43, 5747 (1990)]. Results valid in limit large n, and for finite are presented. An explicit numerical solution to full fourth-order nonlinear equation real-space function f(x) is obtained by truncating at leading nontrivial 1/n. In Fourier space results very good agreement, n as small 5,...

We present calculations for the static and dynamical properties of two parallel double dots, with one extra electron each, constituting a four-dot QCA basic cell. When potential difference is applied to causing switch, we find that on other dot switches accordingly, in response inter-cell Coulomb interactions. include dissipative effects via master equation approach describing time evolution density matrix

We study the phase-ordering dynamics of O(n) model with a conserved order parameter for systems topological defects. present results from both cell dynamical simulations and predictions Gaussian auxiliary field (GAF) approximation XY (n = 2) in two three dimensions, Heisenberg 3) dimensions. describe structure factor S(q) growth law L(t) simulations. The laws obtained are consistent theoretical based on energy-scaling arguments. shows good scaling using length extracted its first moment....

The aim of this work was to design and control, using genetic algorithm (GA) for parameter optimization, one-charge-qubit quantum logic gates σx, σy, σz, two bound states as a qubit space, circular graphene dots in homogeneous magnetic field. method employed the proposed gate implementation is through dynamic control subspace with an oscillating electric field onsite (inside dot) voltage pulse amplitude time width modulation which introduce relative phases transitions between states. Our...

We study the dynamic evolution of charge distribution (polarization) a 2/spl times/2 quantum-dot cell with two electrons in presence time-dependent driver and magnetic field. describe effects flux on response basic dot cell, for fixed, linear switching polarization. In static case, we find that field has strong localizing effect, similar to effect asymmetry. For fixed tunneling, polarization target increases field, going through maximum at particular value cell. ringing decrease final are...

In this work, we propose the generation of a hybrid entangled resource (HER) and its further application in quantum teleportation scheme from an experimentally feasible point view. The source for HER preparation is based on four-wave mixing process photonic crystal fiber, which one party output bipartite state used to herald single photon or added coherent state. From heralded linear optics, created. proposed protocol, Bob uses teleport qubits with different spectral properties. makes Bell...

We demonstrate theoretical stationary and dynamical generation of Bell states in a system two parallel double quantum dots with one mobile electron each (proposed as charge qubits) driven by an external potential difference applied to the second dots. For coherent dynamics, it is shown that four obtained through suitable nonentangled initial condition well control time-dependent electric field. analyze dissipative effects on such state formation, due coupling thermal bath phonons. Via...

We present a quantum teleportation protocol based on hybrid entangled resource (HER) obtained with heralded photons and coherent states. High efficiency of can be by adjusting spectral detection windows.

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