Ja n 20 09 Polarization freezing of 10 4 optically - cooled nuclear spins by coupling to a single electron

The nature of the nano-scale environment presents a major challenge for solid-state implementation of spin-based qubits. In this work, a single electron spin in an optically pumped nanometer-sized III-V semiconductor quantum dot is used to control a macroscopic nuclear spin of several thousand nuclei, freezing its decay and leading to spin life-times exceeding 100 seconds at low temperatures. Few-millisecond-fast optical initialization of the nuclear spin is followed by a slow decay exhibiting random telegraph signals at long delay ∗Current address: Toshiba Research Europe Limited, 260 Cambridge Science Park,Cambridge CB4 0WE, UK