Electromagnetically Induced Transparency Cooling of High-Nuclear-Spin Ions

Area of Science:

• Quantum Information Science
• Atomic Physics
• Laser Cooling

Background:

• Electromagnetically induced transparency (EIT) cooling is vital for trapped-ion quantum computing.
• Complex ground-state level structures in ions like ^{137}Ba^{+} hinder standard EIT cooling by population loss.
• ^{137}Ba^{+} ions with I=3/2 nuclear spin are promising candidates for scalable quantum processors.

Purpose of the Study:

• To develop an effective EIT cooling technique for ^{137}Ba^{+} ions with complex energy levels.
• To demonstrate the cooling of motional modes in single and multi-ion systems.
• To provide a method adaptable for other atomic species with similar level structures.

Main Methods:

• Utilizing an EIT pumping laser to repopulate the cooling subspace and prevent population escape.
• Applying EIT cooling to single ^{137}Ba^{+} ions and a five-ion chain.
• Characterizing the motional state occupation of cooled ions.

Main Results:

• Achieved average motional occupations of 0.08(5) and 0.15(7) for the two radial modes of a single ^{137}Ba^{+} ion.
• Successfully cooled all ten radial modes of a five-ion chain to near their ground states using the same laser parameters.
• Demonstrated a method to overcome population loss in complex atomic systems for efficient cooling.

Conclusions:

• The developed EIT cooling technique effectively cools ^{137}Ba^{+} ions, addressing challenges posed by complex level structures.
• This method is scalable and adaptable for large-scale trapped-ion quantum information processing.
• Engineering the EIT Fano-like spectrum enables simultaneous cooling of multiple modes, enhancing quantum computing applications.