Quantum noise limited and entanglement-assisted magnetometry

Area of Science:

• Atomic physics
• Quantum sensing
• Magnetometry

Background:

• Atomic magnetometers offer high sensitivity for magnetic field detection.
• Fundamental limits in sensitivity are often dictated by projection noise and backaction.
• Quantum phenomena like entanglement can potentially surpass classical sensing limits.

Purpose of the Study:

• To experimentally investigate the fundamental sensitivity limits of atomic radio-frequency magnetometers.
• To demonstrate the enhancement of magnetometer sensitivity using Einstein-Podolsky-Rosen entanglement.
• To achieve quantum-limited sensing with a macroscopic atomic ensemble.

Main Methods:

• Application of an optimal sequence for state preparation, evolution, and backaction evading measurement.
• Generation of Einstein-Podolsky-Rosen entangled atomic states via measurement.
• Utilizing a macroscopic ensemble of 1.5x10^12 atoms for sensing.

Main Results:

• Achieved nearly projection noise limited sensitivity in the atomic magnetometer.
• Demonstrated enhanced sensitivity to pulsed magnetic fields through atomic entanglement.
• Reached a sensitivity of subfemtotesla/sqrt(Hz) using quantum-limited sensing.

Conclusions:

• Optimal control and measurement techniques are crucial for approaching fundamental sensitivity limits.
• Atomic entanglement provides a viable pathway to enhance quantum sensing capabilities.
• Macroscopic atomic ensembles coupled with quantum strategies enable ultra-high sensitivity magnetometry.