# Experimental measurement-device-independent quantum digital signatures over a metropolitan network

## TL;DR

This paper demonstrates a measurement-device-independent quantum digital signature scheme over a large metropolitan network, achieving secure message signing resistant to detector side-channel attacks, and proving its practicality for real-world use.

## Contribution

First field implementation of MDI-QDS over a metropolitan network, showing its feasibility and security against side-channel attacks in practical settings.

## Key findings

- Successfully signed a binary message with a security level of 1E-7
- Demonstrated the practicality of MDI-QDS in a real-world metropolitan network
- Achieved secure quantum digital signatures resistant to detector side-channel attacks

## Abstract

Quantum digital signatures (QDS) provide a means for signing electronic communications with informationtheoretic security. However, all previous demonstrations of quantum digital signatures assume trusted measurement devices. This renders them vulnerable against detector side-channel attacks, just like quantum key distribution. Here, we exploit a measurement-device-independent (MDI) quantum network, over a 200-square-kilometer metropolitan area, to perform a field test of a three-party measurement-device-independent quantum digital signature (MDI-QDS) scheme that is secure against any detector side-channel attack. In so doing, we are able to successfully sign a binary message with a security level of about 1E-7. Remarkably, our work demonstrates the feasibility of MDI-QDS for practical applications.