Experimental quantum Byzantine agreement on a three-user quantum network with integrated photonics.

Area of Science:

• Quantum Information Science
• Network Security
• Quantum Cryptography

Background:

• Scalable and cost-effective quantum communication networks are vital for widespread adoption.
• Existing networks face challenges in security and practical implementation.
• Quantum entanglement is a key resource for secure networked tasks.

Purpose of the Study:

• To establish a complete, scalable, and cost-effective polarization entanglement-based quantum network.
• To demonstrate practical applications like quantum digital signatures and Byzantine agreement.
• To overcome limitations of current quantum network technologies.

Main Methods:

• Utilized an ultrabright integrated Bragg reflection waveguide quantum source.
• Implemented a streamlined polarization analysis module with single-photon detectors.
• Performed continuous quantum entanglement distribution and correlated bit string generation.

Main Results:

• Achieved a fully connected quantum network using polarization entanglement.
• Experimentally implemented source-independent quantum digital signatures using imperfect keys.
• Exceeded the 1/3 fault tolerance bound in Byzantine agreement, ensuring unconditional security.

Conclusions:

• The developed network offers an affordable and practical solution for quantum communication.
• The results pave the way for addressing consensus challenges in quantum networks.
• This work advances the practical deployment of secure quantum communication technologies.