Improved Limits for Violations of Local Position Invariance from Atomic Clock Comparisons.

Area of Science:

• Atomic physics
• Metrology
• Fundamental physics

Background:

• Optical atomic clocks offer unprecedented precision for fundamental physics tests.
• Ytterbium-171 ions ({}^{171}Yb^{+}) provide suitable transitions for high-accuracy optical clocks.

Purpose of the Study:

• To compare two optical clock transitions in {}^{171}Yb^{+} (E2 and E3).
• To determine the frequency ratio between these transitions with high accuracy.
• To test for variations in fundamental constants and their coupling to gravity.

Main Methods:

• Utilized two optical clocks based on the electric quadrupole (E2) and electric octupole (E3) transitions of {}^{171}Yb^{+} ions.
• Measured the frequency ratio ν_{E3}/ν_{E2} using these optical clocks.
• Compared optical clock data with two caesium fountain clocks for absolute frequency determination.
• Analyzed long-term measurements for temporal variations of fundamental constants.

Main Results:

• Measured the frequency ratio ν_{E3}/ν_{E2} = 0.932829404530965376(32), improving previous results by an order of magnitude.
• Determined the absolute optical transition frequency ν_{E3} = 642121496772645.10(8) Hz, the most accurate to date.
• Improved limits on the fractional temporal variation of the fine-structure constant α by a factor of ~20 to 1.0(1.1)×10^{-18}/yr.
• Improved limits on the fractional temporal variation of the proton-to-electron mass ratio μ by a factor of ~2 to -8(36)×10^{-18}/yr.
• Set new limits on the coupling of α and μ to the Sun's gravitational potential.

Conclusions:

• The study demonstrates the high precision achievable with {}^{171}Yb^{+} optical clocks.
• New stringent limits are placed on the variation of fundamental constants, constraining theories beyond the Standard Model.
• The research advances our ability to test fundamental symmetries and the stability of physical laws.