The readout of fullerene-based quantum computing by a scanning tunnelling microscope

We consider the detection of the electron spin of a doped atom, i.e., nitrogen or phosphorus, caged in a fullerene by the currently available technique of the scanning tunnelling microscope (STM), which actually corresponds to the readout of a qubit in fullerene-based quantum computing. Under the conditions of polarized STM current and Coulomb blockade, we investigate the tunnelling matrix elements involving the exchange coupling between the tunnelling polarized electrons and the encapsulated polarized electron, and calculate the variation of the tunnelling current with respect to different orientations of the encapsulated electron spin. The experimental feasibility of our scheme is discussed taking account of some imperfect factors.