Magneto-optical trapping in a near-suface borehole

Area of Science:

• Geophysics
• Quantum Technology
• Atomic Physics

Background:

• Borehole gravity sensing is crucial for subsurface characterization, including mapping rock types and reservoir porosity.
• Quantum gravity sensors offer advantages like faster surveys and less calibration but require miniaturization for borehole deployment.
• Existing quantum sensors need improvements in robustness, size, weight, and power for downhole applications.

Purpose of the Study:

• To demonstrate the first borehole-deployable magneto-optical trap, a key component for cold atom gravity sensors.
• To adapt quantum sensing technology for practical use in downhole environments.
• To lay the groundwork for in-borehole quantum gravity surveys.

Main Methods:

• Developed a compact magneto-optical trap with a radius of 60 mm and length of 890 mm.
• Deployed the trap in a 14 cm wide, 50 m deep borehole to simulate survey conditions.
• Generated clouds of Rubidium-87 (87Rb) atoms at 1-meter intervals.

Main Results:

• Successfully generated atom clouds at 1 m intervals within the simulated borehole environment.
• Produced an average of (3.0 ± 0.1) × 10^5 87Rb atoms per cloud.
• Observed a low standard deviation of 8.9 × 10^4 in atom number across the survey.

Conclusions:

• Demonstrated the feasibility of a borehole-deployable magneto-optical trap for quantum gravity sensing.
• This system represents a significant step towards deploying cold atom-based sensors in downhole applications.
• The results pave the way for enhanced in-borehole gravity surveys with improved accuracy and efficiency.