Approaching the standard quantum limit of a Rydberg-atom microwave electrometer

Area of Science:

• Quantum metrology
• Atomic physics
• Microwave engineering

Background:

• State-of-the-art Rydberg electrometers are limited by thermal atomic motion, falling short of the standard quantum limit.
• Achieving ultimate uncertainty in microwave electrometers is crucial for fundamental and technological advancements.

Purpose of the Study:

• To develop a microwave electrometer with sensitivity approaching the standard quantum limit.
• To investigate the noise limitations and optimization strategies for Rydberg electrometers.

Main Methods:

• Utilized an optically thin medium with approximately 5.2 × 10^5 laser-cooled atoms.
• Implemented microwave heterodyne detection.
• Mitigated various noise sources and optimized electrometer parameters.

Main Results:

• Reduced equivalent noise temperature by a factor of 20.
• Achieved an electric field sensitivity of 10.0 nV cm^-1 Hz^-1/2.
• Reached a performance factor of 2.6 above the standard quantum limit.

Conclusions:

• Demonstrated a significant improvement in Rydberg electrometer sensitivity.
• Provided insights into the capabilities and limitations of Rydberg electrometers.
• Enabled superior detection of weak microwave signals for diverse applications.