Bilinear quantum systems on compact graphs: well-posedness and global exact controllability

TL;DR

This paper extends the theory of bilinear quantum control from intervals to complex networks modeled as graphs, establishing conditions for controllability of quantum particles on these structures.

Contribution

It introduces a mathematical framework for controllability of bilinear Schrödinger equations on graphs, including specific assumptions and applications to star-shaped and tadpole networks.

Findings

Established conditions for global exact controllability on graphs.

Extended controllability theory from intervals to networks.

Applied results to star-shaped and tadpole graph models.

Abstract

A major application of the mathematical concept of graph in quantum mechanics is to model networks of electrical wires or electromagnetic wave-guides. In this paper, we address the dynamics of a particle trapped on such a network in presence of an external electromagnetic field. We study the controllability of the motion when the intensity of the field changes over time and plays the role of control. From a mathematical point of view, the dynamics of the particle is modeled by the so-called bilinear Schr\"odinger equation defined on a graph representing the network. The main purpose of this work is to extend the existing theory for bilinear quantum systems on bounded intervals to the framework of graphs. To this end, we introduce a suitable mathematical setting where to address the controllability of the equation from a theoretical point of view. More precisely, we determine assumptions on the network and on the potential field ensuring its global exact controllability in suitable spaces. Finally, we discuss two applications of our results and their practical implications to two specific problems involving a star-shaped network and a tadpole graph.