  High fidelity qubit readout is critical in order to obtain the thresholds
needed to implement quantum error correction protocols and achieve
fault-tolerant quantum computing. Large-scale silicon qubit devices will have
densely-packed arrays of quantum dots with multiple charge sensors that are, on
average, farther away from the quantum dots, entailing a reduction in readout
fidelities. Here, we present a readout technique that enhances the readout
fidelity in a linear SiMOS 4-dot array by amplifying correlations between a
pair of single-electron transistors, known as a twin SET. By recording and
subsequently correlating the twin SET traces as we modulate the dot detuning
across a charge transition, we demonstrate a reduction in the charge readout
infidelity by over one order of magnitude compared to traditional readout
methods. We also study the spin-to-charge conversion errors introduced by the
modulation technique, and conclude that faster modulation frequencies avoid
relaxation-induced errors without introducing significant spin flip errors,
favouring the use of the technique at short integration times. This method not
only allows for faster and higher fidelity qubit measurements, but it also
enhances the signal corresponding to charge transitions that take place farther
away from the sensors, enabling a way to circumvent the reduction in readout
fidelities in large arrays of qubits.
