Experimental Aspects of Indefinite Causal Order in Quantum Mechanics

TL;DR

This paper reviews experimental approaches to indefinite causal order in quantum mechanics, highlighting advantages in quantum information tasks and discussing techniques, results, and future prospects.

Contribution

It provides a comprehensive overview of experimental methods and theoretical support for realizing indefinite causal order in quantum systems.

Findings

Demonstrated advantages in quantum computation and metrology

Surveyed various experimental techniques and results

Discussed interpretations and future directions

Abstract

In the past decade, the toolkit of quantum information has been expanded to include processes in which the basic operations do not have definite causal relations. Originally considered in the context of the unification of quantum mechanics and general relativity, these causally indefinite processes have been shown to offer advantages in a wide variety of quantum information processing tasks, ranging from quantum computation to quantum metrology. Here we overview these advantages and the experimental efforts to realise them. We survey both the different experimental techniques employed, as well as theoretical methods developed in support of the experiments, before discussing the interpretations of current experimental results and giving an outlook on the future of the field.