# Experimental study of multiple-shot unitary channels discrimination using the IBM Q computers

## TL;DR

This paper experiments with quantum channel discrimination on IBM's quantum computers, showing that simpler circuits perform better in noisy environments.

## Contribution

The study reveals that theoretically optimal quantum circuits are not always best for real-world noisy quantum hardware.

## Key findings

- Deep quantum circuits and high entanglement reduce discrimination performance on IBM Q hardware.
- Circuits with minimal entanglement and limited depth are more resilient to hardware noise.
- Theoretically suboptimal circuits often outperform optimal ones in practical quantum computing.

## Abstract

Tasks involving black boxes appear frequently in the theory of quantum information, with quantum channel discrimination as a central example that has been deeply studied. In this work, we experimentally study the discrimination between two unitary quantum channels in the multiple-shot scenario. We challenge the theoretical results concerning the probability of correct discrimination with the results collected from experiments performed on the IBM Brisbane. Our analysis shows that neither too deep quantum circuits nor circuits that create too much entanglement are suitable for the discrimination task. We conclude that circuit architectures which minimize entanglement overhead while preserving discrimination power are significantly more resilient to hardware noise if their depth does not exceed a threshold value. Consequently, our findings necessitate a paradigm shift: for execution on noisy hardware, the theoretically suboptimal circuit is, counterintuitively, often the superior choice.