Quadrupole Shift Cancellation Using Dynamic Decoupling.

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Metrology
• Spectroscopy

Background:

• Quadrupole shifts cause inhomogeneous broadening in trapped ion crystals, limiting optical ion clock precision to single ions.
• Current limitations in optical ion clocks necessitate the use of single probe ions due to broadening mechanisms.
• The standard quantum limit dictates that using N ions can reduce clock instability by sqrt(N).

Purpose of the Study:

• To present a novel method utilizing radio-frequency pulses to cancel quadrupole shifts in optical clock transitions.
• To enable the use of multiple ions (N>1) in optical clocks, thereby reducing frequency instability.
• To investigate the cancellation of other tensorial shifts and first-order Zeeman shifts.

Main Methods:

• Implementation of a radio-frequency pulse sequence exploiting the tensorial nature of the quadrupole shift.
• Experimental demonstration using correlation spectroscopy on three and seven 88Sr+ ions in a linear Paul trap.
• Application of radio-frequency dynamic decoupling to cancel first-order Zeeman shifts.

Main Results:

• Successful cancellation of quadrupole shifts, reducing the shift difference between ions to approximately 10 mHz.
• Demonstrated cancellation of tensor ac stark shifts alongside quadrupole shifts.
• Experimental validation of the method's effectiveness in a multi-ion system.

Conclusions:

• The developed radio-frequency pulse method effectively cancels quadrupole shifts, a key limitation in optical ion clocks.
• This technique facilitates the use of multiple ions, paving the way for enhanced clock stability beyond the standard quantum limit.
• The method also addresses other systematic errors like tensor ac stark and first-order Zeeman shifts, improving overall clock performance.