Submillihertz magnetic spectroscopy performed with a nanoscale quantum sensor

Area of Science:

• Quantum metrology
• Spectroscopy
• Nanoscale sensing

Background:

• Precise timekeeping is fundamental to metrology and spectroscopy.
• Qubit coherence time traditionally limits clock stability and frequency precision in quantum metrology.
• Stable clocks are crucial for determining standards of time, length, and fundamental constants.

Purpose of the Study:

• To demonstrate a quantum sensing protocol that enhances spectral precision beyond sensor coherence time.
• To show that spectral precision can be limited by classical clock stability.
• To achieve ultra-high frequency resolution in nanoscale magnetic field sensing.

Main Methods:

• Development of a quantum sensing protocol.
• Utilizing a narrow linewidth magnetometer based on single spins in diamond.
• Sensing nanoscale magnetic fields.

Main Results:

• Achieved spectral precision exceeding the sensor coherence time.
• Demonstrated frequency estimation precision scaling as T^{-3/2} for classical oscillating fields.
• Obtained an intrinsic frequency resolution of 607 microhertz, eight orders of magnitude narrower than qubit coherence time.

Conclusions:

• Quantum sensing protocols can overcome intrinsic sensor limitations.
• Classical clock stability is a key factor in achieving ultimate spectral precision.
• Single-spin diamond magnetometers offer a powerful platform for high-resolution nanoscale magnetic field sensing.