QUROPE Quantum Information Processing and Communication in Europe

In a recent publication in Scientific Reports the group led by SOLID partner Jonathan Finley at the Walter Schottky institut of TUM achieve fast, all optical spin control in a single quantum dot without magnetic fields.  The group demonstrated how a precisely timed sequence of monochromatic ultrafast (~ 2–5 ps) optical pulses, with a well defined polarisation can be used to prepare arbitrary superpositions of exciton spin states in a semiconductor quantum dot, achieve ultrafast control of the spin-wavefunction without an applied magnetic field and make high fidelity read-out the quantum state in an arbitrary basis simply by detecting a strong (~ 2–10 pA) electric current flowing in an external circuit. The results obtained show that the combined quantum state preparation, control and read-out can be performed with near-unity (≥97%) fidelity.