Radium Ion Optical Clock.

Area of Science:

• Atomic, Molecular, and Optical (AMO) Physics
• Metrology and Precision Measurement
• Quantum Information Science

Background:

• Optical atomic clocks are crucial for fundamental physics tests and advanced technologies.
• Radium-ion (Ra^{+}) presents a promising candidate for next-generation optical clocks due to its unique atomic properties.
• Previous research has not yet demonstrated an operational Ra^{+} optical clock.

Purpose of the Study:

• To report the first successful operation of a Ra^{+} optical clock.
• To characterize the performance of the Ra^{+} clock in terms of frequency instability and systematic uncertainty.
• To measure fundamental atomic properties using the Ra^{+} clock, such as Landé g-factors.

Main Methods:

• Utilized a single trapped ^{226}Ra^{+} ion.
• Operated the clock on the 7s^{2}S_{1/2}→6d^{2}D_{5/2} electric quadrupole transition.
• Employed self-referencing of symmetric Zeeman transitions to determine frequency instability.
• Evaluated systematic uncertainties and measured Landé g-factor ratios.

Main Results:

• Achieved a frequency instability of 1.1×10^{-13}/sqrt[τ].
• Determined a total systematic uncertainty of Δν/ν=9×10^{-16}.
• Realized the first measurement of the ratio of D_{5/2} to S_{1/2} state Landé g-factors: g_{D}/g_{S}=0.598 805 3(11).

Conclusions:

• The Ra^{+} optical clock is a viable high-performance clock candidate.
• This clock can improve limits on the time variation of the fine-structure constant.
• The Ra^{+} ion possesses features suitable for developing a transportable optical clock.