Correlated charge detection for readout of a solid-state quantum computer

The single-electron transistor (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 subelectron charge motion in the presence of random charging events. We present a detection scheme where the signals from two SETs are cross-correlated to suppress unwanted artifacts due to charge noise. This technique is demonstrated by using the two SETs to detect the charge state of two coupled metal dots, thereby simulating charge transfer and readout in a two-qubit system. These measurements indicate that for comparable buried dopant semiconductor architectures, the minimum measurement time required to distinguish between the two charge states is of the order of 10 ns. (C) 2003 American Institute of Physics.