Inner-shell clock transition in atomic thulium with a small blackbody radiation shift.

Area of Science:

• Atomic Physics
• Quantum Optics
• Metrology

Background:

• Blackbody radiation (BBR) poses a significant systematic error in state-of-the-art optical clocks.
• Reducing BBR effects is crucial for advancing clock precision and accuracy.

Purpose of the Study:

• To investigate the BBR sensitivity of an inner-shell clock transition in neutral thulium (Tm) atoms.
• To explore the potential of Tm-based optical clocks for high-precision measurements.

Main Methods:

• Direct measurement of the differential polarizability of the clock levels in Tm.
• Calculation of the fractional frequency BBR shift based on polarizability measurements.

Main Results:

• Demonstrated unusually low BBR sensitivity for a 1.14 μm inner-shell transition in neutral Tm.
• Inferred a differential polarizability of -0.063(30) atomic units.
• Calculated a fractional frequency BBR shift of 2.3(1.1) × 10^-18 at room temperature, orders of magnitude lower than other neutral atom clocks.

Conclusions:

• The demonstrated low BBR shift in Tm atoms is competitive with state-of-the-art ion clocks.
• This finding enables the development of lanthanide-based optical clocks with relative uncertainties at the 10^-17 level.
• Opens new avenues for high-performance atomic clocks utilizing Tm.