Exploring Spin Mixing with Fluorescence Microscopy

Point defects in diamond, also known as color centers, offer unique possibilities for solid-state quantum magnetometry. Here, we demonstrate and explore quantum spin mixing and optical readout of nitrogen vacancy diamond quantum states with a portable, educational toolkit from Quantum Education Initiative. Visible light photons electronically excite NV centers, upon which their integrated photoluminescence is measured through a free-space photodetector. With household magnets, changes in photoluminescence are correlated with changes in the NV electrons magnetic spin state to intuitively understand optical initialization and readout of an NV ensemble. As a continuous wave laser is used for excitation, we do not demonstrate the trivial procedure for optical readout for quantum gates. Rather, we employ a magnet with a non-zero transverse field component to induce steady-state spin mixing, allowing us to observe decreases in photoluminescence due to occupation of the m s =±1 sublevels.