Single-shot readout of electron spin states in a quantum dot using   spin-dependent tunnel rates
  We present a method for reading out the spin state of electrons in a quantum dot that is robust against charge noise and can be used even when the electron temperature exceeds the energy splitting between the states. The spin states are first correlated to different charge states using a spin dependence of the tunnel rates. A subsequent fast measurement of the charge on the dot then reveals the original spin state. We experimentally demonstrate the method by performing read-out of the two-electron spin states, achieving a single-shot visibility of more than 80%. We find very long triplet-to-singlet relaxation times (up to several milliseconds), with a strong dependence on in-plane magnetic field. 
R. Hanson, L. H. Willems van Beveren, I. T. Vink, J. M. Elzerman, W.   J. M. Naber, F. H. L. Koppens, L. P. Kouwenhoven, and...