Differential-phase-shift quantum key distribution experiment with a planar light-wave circuit Mach-Zehnder...

Area of Science:

• Quantum Information Science
• Optoelectronics
• Photonics

Background:

• Quantum key distribution (QKD) offers secure communication but often requires complex polarization control.
• Planar Light-wave Circuit (PLC) technology enables compact and stable photonic devices.
• Mach-Zehnder interferometers are fundamental components in many optical systems.

Purpose of the Study:

• To investigate the feasibility of a differential-phase-shift QKD system using a PLC Mach-Zehnder interferometer.
• To evaluate the performance of the PLC interferometer in terms of stability and polarization insensitivity.
• To determine the achievable raw key generation rate and quantum bit-error rate over a standard optical fiber.

Main Methods:

• Fabrication of a Mach-Zehnder interferometer using PLC technology.
• Implementation of a differential-phase-shift quantum key distribution protocol.
• Experimental testing of the interferometer's stability and polarization-insensitive operation.
• Transmission of quantum signals over 20 km of optical fiber.

Main Results:

• Stable, polarization-insensitive operation of the PLC Mach-Zehnder interferometer was achieved.
• Raw key creation rate of 3076 bits/s was demonstrated.
• A quantum bit-error rate of 5.0% was recorded over 20 km of fiber.
• The long-term stability of the PLC interferometer was confirmed.

Conclusions:

• PLC technology is suitable for constructing stable and polarization-insensitive interferometers for quantum key distribution.
• The demonstrated system offers a practical approach for high-speed, secure communication.
• Further improvements in interferometer design and error correction could enhance QKD performance.