Lock-in quantum sensing
A synchronized pulse sequence selectively amplifies an oscillating signal.
$$\phi=\gamma\int_0^T y(t)B(t)dt$$
Physical intuition
A synchronized pulse sequence selectively amplifies an oscillating signal.
Deep dive: physical mechanism
Choose pulse spacing so the toggling function overlaps the target AC field, while off-resonant fluctuations average away.
What is measured experimentally?
Signal amplitude is encoded in a final spin population.
Assumptions, noise and limitations
Phase ambiguity and bandwidth–sensitivity tradeoffs require calibration.
Research and simulation exercise
Sweep AC frequency and plot the sensor transfer function.
Connect the ideas
Explore the chapter overview, learning path, and references.