XXXVI Reunión Bienal de la Real Sociedad Española de Física

Single-atom edgelike states via quantum interference

18 jul. 2017 17:45

20m

Aula Química General (Facultad Química (USC))

Oral parallel contribution Quantum and Non-linear Optics Quantum Technologies: joint symposium of the Quantum Information and Quantum and Non-linear Optics specialised groups

Descripción

Recent theoretical and experimental studies have shown that it is possible to simulate artificial magnetic fields with ultracold atoms in optical lattices [1]. In particular, the possibility to implement chiral, topologically protected edge states analogous to those found in the context of quantum Hall physics has been demonstrated both for fermionic and bosonic atoms [2,3]. In this work, we propose an alternative strategy to implement robust edgelike states (ELS) in optical ribbons, which we model by regarding each of the sites as a two-dimensional harmonic trap of equal frequency, with a single atom carrying l = 0 or l = 1 orbital angular momentum (OAM) units. First, we consider a system of three in-line sites governed by tunneling dynamics, which can be described by a few-state model. We show that in this system quantum interference effects give rise to spatial dark states (SDS), i.e., states in which one site remains unpopulated along the time evolution. Then, we show that by using the SDS as basic building blocks, global ELS can be created in arbitrarily large ribbons. These ELS are very robust against defects in the ribbon and perturbations in the phase differences between the local eigenstates of the sites required to have quantum interference [3]. For the l = 0 case, the tunneling amplitudes between sites are always real and interference effects are solely induced by phase differences between the populated sites. This fact allows one to create ELS within this manifold and switch between them in a very straightforward manner by applying laser pulses, as shown in the left panel of figure 1, and also opening the possibility to implement similar ELS in more complex geometries. For the l = 1 case, the few-state description is richer because the tunneling amplitudes depend both on the spatial localization and the winding number of the local states, and they may become complex depending on the relative position of the sites [4]. The ELS implemented in this manifold can display global chirality, as shown in the right panel of figure 1. Another interesting possibility that this manifold offers is to simulate an extra dimension by regarding the winding number as a synthetic dimension.