Colloidal quantum dots grown from singly-doped seed clusters: a spin-photon interface for quantum memories and quantum repeaters

Singly doped colloidal quantum dots (CQDs) are promising spin-photon interfaces for quantum memories and quantum repeaters. Coupling between the dopant spin and the band edge CQD exciton substantially enhances the optical interaction cross-section for the former. As substrate-free nanocrystals, CQDs can be manipulated by pick-and-place nano-positioning techniques for straightforward device incorporation. They also benefit from a suite of well-developed synthetic techniques that enable their structure and composition to be controlled for enhanced spin lifetime and to tune their optical properties. Single doping of CQDs has relied on stochastic processes, resulting in a distribution of the number of dopants per CQD and the random positioning of the dopant within the CQD. However, the deterministic doping of InP/ZnSeS core/shell CQDs with a single Mn has recently been demonstrated via growth from molecular seed clusters including a single Mn atom. Here the optical properties of these deterministically doped CQDs are reported. The photoluminescence (PL) spectra of the doped and undoped CQDs are compared, enabling the contribution of the dopant to the emission to be identified. Further, the dependence of their PL transients on temperature and emission wavelength is used to study energy transfer between the band edge of the CQD and the dopant.