Detecting factorization effect in continuous-time quantum walks

We consider an continuous-time quantum walk on triple graphs with a potential well in one of the terminal sites on the main chain and study its dynamical properties in the open system by introducing a ‘spontaneous damping’ process between the terminal site and its nearest neighbour one. Calculating the stable probability of the terminal site and the time evolution of probabilities of the other sites on the main chain, we show that the system can manifest the factorization and coherence protection phenomena when the length and position of the side chain satisfy some concrete conditions. Furthermore we investigate the effect of disorder on the hopping strength and show that the existence of the disorder can destroy the coherence protection phenomena and increase the stable probability of the terminal site on the main chain.

Coupling quantum corrals to form artificial molecules

Quantum corrals can be considered artificial atoms. By coupling many quantum corrals together, artificial matter can be created at will. The atomic scale precision with which the quantum corrals can be made grants the ability to tune parameters that are difficult to control in real materials, such as the symmetry of the states that couple, the on-site energy of these states, the hopping strength and the magnitude of the orbital overlap. Here, we systematically investigate the accessible parameter space for the CO on Cu(111) platform by constructing (coupled) quantum corrals of different sizes and shapes. By changing the configuration of the CO molecules that constitute the barrier between two quantum corrals, the hopping integral can be tuned between 0 and -0.3 eV for s- and p-like states, respectively. Incorporation of orbital overlap is essential to account for the experimental observations. Our results aid the design of future artificial lattices.

EVOLUTION OF ATOM-FIELD PROBABILITY IN A COUPLED CAVITY SYSTEM

In this paper we have investigated the dynamics of two cavities each with a two-level atom, coupled together with photon hopping. The coupled cavity system is studied in single excitation subspace and the evolution of the atom (field) states probabilities are obtained analytically. The probability amplitude of states executes oscillations with different modes and amplitudes, determined by the coupling strengths. The evolution is examined in detail for different atom field coupling strength, g and field–field hopping strength, A. It is noticed that the exact atomic probability amplitude transfer occurs when g ≪ A with minimal field excitation probability and the period of probability transfer is calculated. In the limit g ≫ A there exists periodic exchange of probability between atom and field inside each cavity and also between cavity 1 and cavity 2. Periodicity of each exchange in this limit also obtained.

TOPOLOGICAL EFFECT ON PERSISTENT CURRENTS AND THE SIGN OF LOW-FIELD CURRENTS IN n-FOLD TWISTED MOEBIUS STRIPS

I investigate persistent currents and the sign of these currents in a low-field limit (ϕ→0) for n-fold twisted Moebius strips threaded by a slowly varying magnetic flux ϕ and describe the effects of the total number of electrons Ne, chemical potential μ, number of twists n, and disorder on these quantities. Transverse hopping strength (v⊥) of the electrons plays an important role in the periodicity of the persistent current. It is observed that for Moebius strips with an odd number of twists the current shows ϕ0/2 flux-quantum periodicity only when v⊥=0, but if the electrons are allowed to hop along the transverse direction, then current shows ϕ0 flux periodicity for both odd- and even-fold twisted Moebius strips. The sign of the low-field currents also has strong dependence on the number of twists n. For zero transverse hopping strength (v⊥ = 0) the sign of the currents can be predicted exactly in odd-fold twisted Moebius strips that are characterized by fixed Ne only. For impurity free systems, the current shows only diamagnetic sign irrespective of Ne, i.e., whether the systems contain odd or even Ne. In the presence of impurity, the current shows diamagnetic and paramagnetic sign, respectively, for the systems with odd and even Ne. On the other hand, for non-zero transverse hopping strength (v⊥≠0), the sign of the low-field currents cannot be predicted exactly. Then it strongly depends on Ne, μ, and the specific realization of disordered configurations.