Self-testing mutually unbiased bases in higher dimensions with space-division multiplexing optical fiber technology

TL;DR

This paper demonstrates the experimental self-testing of mutually unbiased bases in higher dimensions using space-division multiplexing optical fiber technology, validating quantum device performance without detailed device models.

Contribution

It introduces a novel experimental implementation of self-testing MUBs in higher dimensions with advanced optical fiber technology, enabling device certification in quantum information.

Findings

Successfully self-tested two four-dimensional MUBs.

Achieved high optical mode overlap for reliable self-testing.

Quantified measurement incompatibility and randomness extraction.

Abstract

In the device-independent quantum information approach, the implementation of a given task can be self-tested solely from the recorded statistics and without detailed models for the employed devices. Even though experimentally demanding, it provides appealing verification schemes for advanced quantum technologies that naturally fulfil the associated requirements. In this work, we experimentally study whether self-testing protocols can be adopted to certify the proper functioning of new quantum devices built with modern space-division multiplexing optical fiber technology. Specifically, we consider the prepare-and-measure protocol of M.~Farkas and J.~Kaniewski (Phys.~Rev.~A 99, 032316) for self-testing measurements corresponding to mutually unbiased bases (MUBs) in a dimension $d>2$. In our scheme, the state preparation and measurement stages are implemented with a multi-arm interferometer built with new multi-core optical fibers and related components. Due to the high-overlap of the interferometer's optical modes achieved with this technology, we are able to reach the required visibilities for self-testing the implementation of two four-dimensional MUBs. We also quantify two operational quantities of the measurements: (i) the incompatibility robustness, connected to Bell violations, and (ii) the randomness extractable from the outcomes. Since MUBs lie at the core of several quantum information protocols, our results are of practical interest for future quantum works relying on space-division multiplexing optical fibers.