  We present a new way of continuously reading-out the state of a single
electronic spin. Our detection scheme is based on an exchange interaction
between the electronic spin and a nearby read-out quantum dot. The coupling
between the two systems results in a spin-dependent conductance through the
read-out dot and establishes an all electrical and non-destructive single spin
detection. With conductance variations up to 4% and read-out fidelities greater
than 99.5%, this method represents an alternative to systems where spin to
charge conversion cannot be implemented. Using a semi-classical approach, we
present an asymetric exchange coupling model in good agreement with our
experimental results.
