Double quantum magnetometry at large static magnetic fields

We present a protocol to achieve double quantum magnetometry at large static magnetic fields. This is a regime where sensitive sample parameters, such as the chemical shift, get enhanced facilitating their characterization. In particular, our method delivers two-tone stroboscopic radiation patterns with modulated Rabi frequencies to achieve larger spectral signals. Furthermore, it does not introduce inhomogeneous broadening in the sample spectrum preventing signal misinterpretation. Moreover, our protocol is designed to work under realistic conditions such as the presence of moderate microwave power and errors on the radiation fields. Albeit we particularize to nitrogen vacancy centers, our protocol is general, thus applicable to distinct quantum sensors.

Figure 1

(a) Top-hat $\mathrm{\Omega }$ leading to ${\tilde{U}}_{[\pi ,0]}^{[+1,-1,+1]}$ and ${\tilde{U}}_{[\pi ,\pi /2]}^{[-1,+1,-1]}$. (b) Pulse structure of the sequence we repeat in our numerical simulations. (c) $f_{37,43}\left(r\right)$ (dark and clear curves, respectively). Yellow square and diamond mark the values of $f_{43}\left(r\right)$ we use in the next figure. (d) Computed signal for instantaneous $\pi$ pulses (clear-green curve) and for finite-width pulses (curve over dark-green area). Blue square and diamond mark the theoretically expected signal.

Figure 2

Solid red curves (wide curves) correspond to ideal SQM schemes (i.e., these signals appear after applying instantaneous $\pi$ pulses). Thin red lines are the signals appearing with DQM with instantaneous $\pi$ pulses, while circles and squares have been obtained with the modulated $\mathrm{\Omega }\left(t\right)$ in inset 1. Inset 2: Emergence of a secondary peak. Note that this does not occur in the case of our DQM schemes with tailored $\mathrm{\Omega }\left(t\right)$.