Comparative analysis of quantum two-way time transfer and quantum round-trip time transfer in consistent...

Area of Science:

• Quantum physics
• Metrology
• Information science

Background:

• Precise time transfer is crucial for modern technologies.
• Quantum time transfer protocols offer enhanced security and accuracy.
• Comparing quantum two-way time transfer (Q-TWTT) and quantum round-trip time transfer (Q-RTTT) is essential for practical implementation.

Purpose of the Study:

• To experimentally compare the performance of Q-TWTT and Q-RTTT.
• To evaluate time transfer accuracy and stability under consistent conditions.
• To determine the advantages of Q-TWTT for practical applications.

Main Methods:

• Utilized a single energy-time entangled biphoton source.
• Conducted experiments over fiber links of 11.3 km, 22.4 km, and 55.6 km.
• Ensured uniform photon counts and measured standard deviations (SDs) and time deviations (TDEV).

Main Results:

• Q-TWTT demonstrated smaller SDs (0.46 ps to 3.98 ps) compared to Q-RTTT (0.65 ps to 4.39 ps) across all fiber lengths.
• Q-TWTT showed better long-term stability with lower TDEV values (0.49 ps to 1.01 ps) versus Q-RTTT (0.63 ps to 1.36 ps).
• Results align with theoretical predictions, with Q-TWTT's superiority attributed to system symmetry.

Conclusions:

• Q-TWTT exhibits superior time transfer performance over Q-RTTT.
• The enhanced performance of Q-TWTT is due to protocol-specific factors, particularly system symmetry.
• Q-TWTT presents significant advantages for practical, high-precision time synchronization applications.