Absolute clock synchronization with a single time-correlated photon pair source over a 10 km optical fibre

Area of Science:

• Quantum Information Science
• Optical Metrology
• Network Synchronization

Background:

• Accurate clock synchronization is crucial for distributed systems and scientific experiments.
• Existing methods often face limitations in distance independence, security against delay attacks, or scalability.
• Quantum phenomena offer potential for enhanced synchronization precision and security.

Purpose of the Study:

• To demonstrate a novel point-to-point clock synchronization protocol.
• To achieve distance-independent absolute clock synchronization secure against symmetric delay attacks.
• To enable scalable synchronization of multiple clocks using a single source.

Main Methods:

• Utilizing bidirectionally propagating photon pairs from a single spontaneous parametric down-conversion (SPDC) source.
• Leveraging tight timing correlations between photon pairs to measure single and round-trip times.
• Employing photons reflected from the end of a 10 km telecommunications fiber to derive synchronization signatures.

Main Results:

• Successful demonstration of a distance-independent absolute clock synchronization protocol.
• Achieved synchronization security against symmetric delay attacks.
• Showcased the ability to derive round-trip time signatures from reflected photons without extra optics.
• Validated a client-server configuration for synchronizing multiple clocks with a single reference source.

Conclusions:

• The developed protocol offers a robust and secure method for absolute clock synchronization.
• The technique is scalable for synchronizing networks of clocks without requiring multiple entangled photon sources.
• This approach has significant implications for quantum communication networks and distributed sensing.