<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mrow><mml:mi mathvariant="normal">N</mml:mi></mml:mrow></mml:mrow></mml:math> - <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>V</mml:mi></mml:math> –Diamond Magnetic Microscopy Using a Double Quantum 4-Ramsey Protocol

We introduce a double quantum (DQ) 4-Ramsey measurement protocol that enables wide-field magnetic imaging using nitrogen-vacancy ($\mathrm{N}$-$V$) centers in diamond, with enhanced homogeneity of the sensitivity relative to conventional single (SQ) techniques. The DQ employs microwave-phase alternation across four consecutive Ramsey (4-Ramsey) measurements isolate desired signal from any residual SQ induced by microwave pulse errors. In demonstration experiment employing 1-$\ensuremath{\mu}\mathrm{m}$-thick $\mathrm{N}$-$V$ layer macroscopic diamond chip, provides volume-normalized dc ${\ensuremath{\eta}}^{V}=34\phantom{\rule{0.2em}{0ex}}\mathrm{nT}\phantom{\rule{0.1em}{0ex}}{\mathrm{Hz}}^{\ensuremath{-}1/2}\phantom{\rule{0.1em}{0ex}}\ensuremath{\mu}{\mathrm{m}}^{3/2}$ $125\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}\ifmmode\times\else\texttimes\fi{}125\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$ field view, about $5\ifmmode\times\else\texttimes\fi{}$ less spatial variation view compared measurement. improved robustness and dynamic broadband sources such as integrated circuits electrically active cells.