Quantum Walks with Non-Orthogonal Position States

TL;DR

This paper develops a framework for quantum walks with non-orthogonal position states, enabling new experimental possibilities and control over state properties by mapping them to standard orthogonal quantum walks.

Contribution

It introduces a general description and a mapping method for non-orthogonal quantum walks, expanding experimental capabilities and control over quantum state dynamics.

Findings

Mapping non-orthogonal to orthogonal states enables use of existing tools.

Tuning non-orthogonality facilitates preparation of extended states.

Adjusting momentum shifts allows control of walk velocity and exploration of Bloch oscillations.

Abstract

Quantum walks have by now been realized in a large variety of different physical settings. In some of these, particularly with trapped ions, the walk is implemented in phase space, where the corresponding position states are not orthogonal. We develop a general description of such a quantum walk and show how to map it into a standard one with orthogonal states, thereby making available all the tools developed for the latter. This enables a variety of experiments, which can be implemented with smaller step sizes and more steps. Tuning the non-orthogonality allows for an easy preparation of extended states such as momentum eigenstates, which travel at a well-defined speed with low dispersion. We introduce a method to adjust their velocity by momentum shifts, which allows to investigate intriguing effects such as the analog of Bloch oscillations.