An ensemble of coherently interacting spins can host spectacular examples of spontaneous and driven quantum many-body phases, such as superradiance and time crystals. Further, if one can access coherently the quanta of such ensembles they can be exploited for quantum computational tasks and for the storage of quantum information in collective modes of the ensemble—a quantum memory. In semiconductor quantum dots, a single electron spin is a coherent interface to an isolated ensemble of nuclear spins. In an optically active quantum dot system, we have used all-optical techniques to show (i) coherent injection of nuclear spin-waves [1], (ii) sensing of a coherent single nuclear-spin excitation [2], and (iii) the presence of nuclear entanglement as a dark many-body state [3]. Combined with the exquisite quantum optical properties of quantum dots, these results open a new avenue for state engineering of a mesoscopic ensemble of spins connected to single photons, as promising towards quantum simulation, computation, and communication. [1] Gangloff et al. (2019), Science 364 [2] Jackson et al. (2021), Nat. Phys. 17 (5) [3] Gangloff et al. (2021), Nat. Phys. (In press)

Dorian Gangloff got his PhD in Physics at MIT in 2016, working in the group of Prof. Vladan Vuletic on simulations of nano-friction with ultracold trapped ions. Since then, he has been a postdoctoral research fellow at the Cavendish Laboratory at the University of Cambridge, working in the group of Prof. Mete Atature on quantum information science with solid-state spins in semiconductors. In October 2021, he will begin a principal investigator position as a Royal Society University Research Fellow, and will start his own group in the department of Engineering Science at the University of Oxford in January 2022.