# Pre- and post-selection paradoxes in quantum walks

## TL;DR

This paper explores pre- and post-selection paradoxes in quantum walks, demonstrating their connection to contextuality and non-classical behavior, thus providing evidence against macro-realistic classical explanations.

## Contribution

It introduces new paradox scenarios in quantum walks that serve as proofs of contextuality, extending previous results and deepening understanding of quantum non-classicality.

## Key findings

- Quantum walk paradoxes demonstrate contextuality.
- Certain measurement sequences defy classical macro-realistic models.
- The work links paradoxes to fundamental non-classical features.

## Abstract

Many features of single-partite quantum walks can be simulated by classical waves. However, it was recently experimentally shown that some temporal sequences of measurements on a quantum walker do not admit a classical description in terms of macro-realistic theories. Here, we extend this observation and present pre- and post-selection scenarios in quantum walks leading to logical paradoxes. Such paradoxes were recently shown to be equivalent to proofs of contextuality, therefore we provide an additional argument for non-classicality of a quantum walk model. The assumptions behind the claims of non-classicality (including contextuality and violations of macro-realism) are also discussed.