This invention can be used for the measurement of weak electric and magnetic fields at the nanometer scale in fields ranging from materials science to fundamental physics and biomedical science.
Quantum probes can measure time-varying fields with high sensitivity and spatial resolution, but existing measuring techniques are limited to the measurement of constant (DC) or oscillating (AC) parameters. Therefore, there is a need for a method of measuring time-varying fields with unknown dynamics.
The invention is a method to efficiently reconstruct arbitrary time dependence of external parameters by manipulation of the quantum probe with Walsh-function-based pulsed control. Control pulses generate digital filters that extract information about the variation of the external parameter in the time domain and allow reconstructing its waveform. The system is implemented using a diamond structure that includes nitrogen-vacancy (NV) centers for sensing magnetic and electric fields. An arbitrary waveform generator and microwave waveguides manipulate the quantum spins in the diamond structure using a plurality of coherent control sequences to measure the arbitrary profile of time-varying magnetic fields. A laser optically addresses the quantum spins in the diamond structure for initialization and readout.
This approach provides accurate and efficient reconstruction in the time domain with minimal reconstruction error.
The control technique used is robust against dephasing noise, as it acts as a dynamical decoupling (DD) sequence.