Analysis and minimization of bending losses in discrete quantum networks

Abstract

We study theoretically the transfer of quantum information along bends in two-dimensional discrete lattices. Our analysis shows that the fidelity of the transfer decreases considerably, as a result of interactions in the neighbourhood of the bend. It is also demonstrated that such losses can be controlled efficiently by the inclusion of a defect. The present results are of relevance to various physical implementations of quantum networks, where geometric imperfections with finite spatial extent may arise as a result of bending, residual stress, etc

Transfer of optical signals around bends in two-dimensional linear photonic networks

“…As explained in Ref. [22], for such a type of Hamiltonians a corner defect minimizes the bending losses by rearranging the spectrum that has been distorted by the bend. To confirm this once more, in Fig.…”

“…The regime of bend angles for which this approximation is justified could not be assessed within the generic model of Ref. [22], since it depends strongly on the details of the physical system under consideration. One of the purposes of the present work is to address this question, in the framework of a considerably more elaborate theoretical model that pertains to a two dimensional (2D) linear PL with engineered couplings, taking into account possible anisotropy effects.…”

Selective dynamical decoupling for quantum state transfer

“…If there is a bend in the chain at qubit α, it is conceivable that the coupling strength between the two neighbouring qubits at the bend becomes large enough so that it is no longer negligible (compare with figure 1). This type of perturbation and its effects have been studied in detail in [10]. It has been shown that such an interaction has severe detrimental effects on quantum state transfer in this network.…”

“…In [10] it has been demonstrated that the effect of the perturbing additional coupling at the bend of a linear qubit chain diminishes with increasing numbers N of qubits of the chain. In view of the linearly increasing number of pulses necessary to counteract the influence of the disturbance we expect that for very long qubit chains the effort required to successfully implement decoupling may no longer be worth the expected benefits.…”

“…In such a case additional strong couplings between qubits may arise close to the position of the bend so that simple one-dimensional models with nearest-neighbour couplings no longer describe these situations adequately. Such configurations have been studied recently in detail [10]. In particular, it has been demonstrated that the additional interactions arising from qubits close to the position of the bend significantly affect quantum state transfer in a detrimental way.…”