# Quantum communication protocols as a benchmark for quantum computers

## TL;DR

This paper demonstrates how quantum communication protocols can serve as benchmarks for quantum computers, highlighting their capabilities in information transfer, entanglement storage, and error mitigation on superconducting processors.

## Contribution

It provides proof-of-principle implementations of superdense coding and BB84 protocols on IBM quantum processors, exploring their potential as benchmarks for quantum hardware performance.

## Key findings

- Successful implementation of superdense coding and BB84 protocols.
- Quantum devices can transfer information efficiently between distant qubits.
- Error mitigation improves communication protocol results.

## Abstract

We point out that realization of quantum communication protocols in programmable quantum computers provides a deep benchmark for capabilities of real quantum hardware. Particularly, it is prospective to focus on measurements of entropy-based characteristics of the performance and to explore whether a "quantum regime" is preserved. We perform proof-of-principle implementations of superdense coding and quantum key distribution BB84 using 5- and 16-qubit superconducting quantum processors of IBM Quantum Experience. We focus on the ability of these quantum machines to provide an efficient transfer of information between distant parts of the processors by placing Alice and Bob at different qubits of the devices. We also examine the ability of quantum devices to serve as quantum memory and to store entangled states used in quantum communication. Another issue we address is an error mitigation. Although it is at odds with benchmarking, this problem is nevertheless of importance in a general context of quantum computation with noisy quantum devices. We perform such a mitigation and noticeably improve some results.