Single electron devices for simulating read-out in a solid state quantum computer

The radio frequency single electron transistor (rf-SET) is a prime candidate for reading out the final state of a qubit in a solid state quantum computer. Such a measurement requires the detection of sub-electron charge motion in the presence of random charging-decharging events associated with traps in the neighboring material system and SET tunnel junctions. Here we present a detection scheme together with experimental data from two dc-SETs where the signals from each are cross-correlated both temporally and spatially to suppress uncorrelated events arising from charge traps in the substrate and oxide. The technique is demonstrated using two dc-SETs that can detect the charge-state of two coupled metal dots, simulating charge transfer and read-out in a two-qubit system. In an effort towards operating the correlated detection scheme on microsecond time-scales, we have demonstrated an ability to detect controlled single electron transfer using an rf-SET. (C) 2003 Published by Elsevier Science B.V.