Direct measurement of hyperfine shifts and radio frequency manipulation of the nuclear spins in individual CdTe/ZnTe quantum dots

We achieve direct detection of electron hyperfine shifts in individual CdTe / ZnTe quantum dots. For the previously inaccessible regime of strong magnetic fields Bz≳0.1T, we demonstrate robust polarization of a few-hundred-particle nuclear spin bath, with an optical initialization time of ∼1 ms and polarization lifetime exceeding ∼1s. Nuclear magnetic resonance spectroscopy of individual dots reveals strong electron-nuclear interactions characterized by Knight fields |Be|≳50 mT, an order of magnitude stronger than in III–V semiconductor quantum dots. Our studies confirm II–VI semiconductor quantum dots as a promising platform for hybrid electron-nuclear spin qubit registers, combining the excellent optical properties comparable to III–V dots and the dilute nuclear spin environment similar to group-IV semiconductors.