Certifying high-dimensional quantum channels

TL;DR

This paper introduces efficient methods to certify the dimensionality of high-dimensional quantum channels, demonstrated experimentally with optical fibers, advancing quantum communication technology.

Contribution

It develops new certification techniques for high-dimensional quantum channels, including a notion of channel dimensionality and practical witnesses for various trust scenarios.

Findings

Certified dimensionalities up to 59 in optical fibers

Developed practical certification methods for high-dimensional channels

Provided an accurate noise model through numerical simulations

Abstract

The use of high-dimensional systems for quantum communication opens interesting perspectives, such as increased information capacity and noise resilience. In this context, it is crucial to certify that a given quantum channel can reliably transmit high-dimensional quantum information. Here we develop efficient methods for the characterization of high-dimensional quantum channels. We first present a notion of dimensionality of quantum channels, and develop efficient certification methods for this quantity. We consider a simple prepare-and-measure setup, and provide witnesses for both a fully and a partially trusted scenario. In turn we apply these methods to a photonic experiment and certify dimensionalities up to 59 for a commercial graded-index multi-mode optical fiber. Moreover, we present extensive numerical simulations of the experiment, providing an accurate noise model for the fiber and exploring the potential of more sophisticated witnesses. Our work demonstrates the efficient characterization of high-dimensional quantum channels, a key ingredient for future quantum communication technologies.