The atomic fabrication of a silicon based quantum computer

This paper presents recent results on two different approaches to realize a solid-state quantum computer based in silicon, using phosphorus atoms as qubits. In the first approach the device is built from the 'bottom-up using a combination of atomic lithography with a scanning tunneling microscope and high quality silicon epitaxial growth using molecular beam epitaxy. In the second approach ion implantation is used to implant the phosphorus atoms from the 'top-down'. In both cases surface control electrodes are fabricated by conventional electron beam lithography. Techniques for qubit read-out utilising coincidence measurements on twin single electron transistors are also presented.