Adsorption of Pd, Pt, Cu, Ag, and Au monomers on NiAl(110) surface: a comparative study from DFT calculations.

First principles calculations based on periodic density functional theory (DFT) have been used to investigate the structural, energetic and electronic properties of different transition metal atoms (Pd, Pt, Cu, Ag, and Au) on the NiAl(110) surface at low coverages (0.08 and 0.25 monolayer). All adatoms prefer to adsorb on 4-fold coordinated sites interacting with two Al and two Ni atoms and forming polar and covalent bonds, respectively. The calculated negative work function changes are explained by the effect of positive surface image created after adsorption, which induces the polarization of the negatively charged adsorbates. Consequently, for metals with similar electronegativity as Ni (Ag and Cu), this polarization effect becomes more significant and leads to larger negative work function changes, but the charge transferred is small.

Dynamically disordered quantum walk as a maximal entanglement generator.

We show that the entanglement between the internal (spin) and external (position) degrees of freedom of a qubit in a random (dynamically disordered) one-dimensional discrete time quantum random walk (QRW) achieves its maximal possible value asymptotically in the number of steps, outperforming the entanglement attained by using ordered QRW. The disorder is modeled by introducing an extra random aspect to QRW, a classical coin that randomly dictates which quantum coin drives the system's time evolution. We also show that maximal entanglement is achieved independently of the initial state of the walker, study the number of steps the system must move to be within a small fixed neighborhood of its asymptotic limit, and propose two experiments where these ideas can be tested.