Free-Space and Fiber-Integrated Measurement-Device-Independent Quantum Key Distribution under High Background Noise

Area of Science:

• Quantum communication
• Quantum cryptography
• Network security

Background:

• Measurement-device-independent quantum key distribution (MDI QKD) is crucial for secure quantum networks.
• Implementing MDI QKD during daytime is challenging due to high background noise.
• Existing protocols like BB84 struggle under such conditions, even with ideal sources.

Purpose of the Study:

• To demonstrate a robust MDI QKD system operational during daytime.
• To establish a hybrid quantum communication network integrating free-space and fiber channels.
• To explore the feasibility of Hong-Ou-Mandle interference with moving satellites for space-ground networks.

Main Methods:

• Developed and implemented a measurement-device-independent quantum key distribution protocol resilient to daytime background noise.
• Integrated free-space and fiber optic channels using Hong-Ou-Mandle (HOM) interference to create a hybrid quantum network.
• Investigated the application of HOM interference principles for satellite-based quantum communication.

Main Results:

• Successfully demonstrated MDI QKD during daytime, a significant advancement over previous limitations.
• Established a functional hybrid quantum network linking different transmission media.
• Confirmed the potential for using HOM interference in mobile satellite quantum communication scenarios.

Conclusions:

• The demonstrated daytime MDI QKD is a key step towards global quantum networks.
• Hybrid network integration via HOM interference offers a scalable solution for quantum communication.
• This research lays the groundwork for future integrated space-ground quantum communication systems with enhanced security.