Stable, low-error, and calibration-free polarization encoder for free-space quantum communication

Area of Science:

• Quantum Information Science
• Free-Space Quantum Communication
• Optical Engineering

Background:

• Free-space quantum communication relies on quantum state sources with precise control over polarization.
• Existing polarization encoders often suffer from calibration drift and limited long-term stability, hindering practical applications.
• A stable, calibration-free source is crucial for robust quantum key distribution and other quantum communication protocols.

Purpose of the Study:

• To present a novel polarization encoder for free-space quantum communication.
• To demonstrate a device that generates predetermined polarization states with a fixed reference frame.
• To achieve long-term stability and eliminate the need for transmitter/receiver calibration.

Main Methods:

• Development of a novel polarization encoder architecture.
• Integration of the encoder into a free-space optical setup.
• Experimental validation through a proof-of-concept demonstration.

Main Results:

• The proposed encoder generates predetermined polarization states in a fixed reference frame.
• The device exhibits long-term stability without requiring active calibration.
• A quantum bit error rate below 0.2% was maintained for several hours.

Conclusions:

• The developed polarization encoder offers a stable and reliable solution for quantum communication.
• Eliminating calibration requirements simplifies system deployment and enhances operational robustness.
• This technology paves the way for more practical and widespread free-space quantum communication systems.