Test of Special Relativity Using a Fiber Network of Optical Clocks.

Area of Science:

• Fundamental Physics
• Relativity
• Metrology

Background:

• High-accuracy atomic clocks are crucial for testing fundamental physics.
• Optical fiber links allow precise comparison of clocks over long distances.

Purpose of the Study:

• To test time dilation predicted by special relativity using a network of strontium optical lattice clocks.
• To improve the constraint on the Robertson-Mansouri-Sexl parameter (|α|) using precise clock comparisons.

Main Methods:

• Utilized phase-compensated optical fiber links to connect four strontium optical lattice clocks across Europe.
• Monitored daily frequency differences between the clocks to search for variations predicted by relativistic effects.
• Applied advanced data analysis to achieve unprecedented statistical resolution.

Main Results:

• Achieved a new constraint on the Robertson-Mansouri-Sexl parameter: |α|≲1.1×10^{-8}.
• Improved the best known constraint on time dilation violation by a factor of approximately 2 compared to Ives-Stilwell experiments.
• Surpassed previous atomic clock comparison constraints by two orders of magnitude.

Conclusions:

• This study represents a new generation of fundamental physics tests leveraging optical clocks and fiber links.
• The improved constraint on |α| strengthens tests of special relativity's time dilation.
• Future advancements in clock accuracy and fiber link operation promise further orders-of-magnitude improvements in these tests.