High fidelity measurement of singlet–triplet state in a quantum dot

We demonstrate experimentally a read‐out method that distinguishes between two‐electron spin states in a quantum dot. This scheme combines the advantages of the two existing mechanisms for spin‐to‐charge conversion with single‐shot charge detection: a large difference in energy between the two states and a large difference in tunnel rate between the states and a reservoir. As a result, a spin measurement fidelity of 97% was achieved, which is much higher than previously reported fidelities. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)