Quantum key distribution with entangled photons generated on demand by a quantum dot.

Area of Science:

• Quantum Information Science
• Quantum Communication
• Solid-State Physics

Background:

• Quantum key distribution (QKD) is fundamental for secure quantum networks.
• Entanglement-based QKD offers enhanced security and scalability but requires advanced photon sources.
• Semiconductor quantum emitters present a viable solution for on-demand, high-fidelity entangled photon generation.

Purpose of the Study:

• To demonstrate a modified Ekert quantum key distribution protocol using a semiconductor quantum dot.
• To test the protocol's feasibility in realistic communication channels, including fiber and free space.
• To highlight the readiness of quantum-dot technology for practical quantum communication.

Main Methods:

• Utilized a coherently driven quantum dot as a source of entangled photons.
• Implemented a modified Ekert QKD protocol.
• Conducted experiments over a 250-m single-mode fiber and through free space between two campus buildings.

Main Results:

• Successfully demonstrated QKD using entangled photons from a quantum dot.
• Validated the performance of the quantum-dot source in both fiber and free-space channels.
• Showcased low multiphoton emission, enhancing security against eavesdropping.

Conclusions:

• Quantum-dot entangled photon sources are mature for real-world quantum communication applications.
• The study validates the practical implementation of entanglement-based QKD outside of controlled laboratory environments.
• This work advances the deployment of secure quantum networks using scalable semiconductor technology.