  We propose a solid-state experiment to study the process of continuous
quantum measurement of a qubit state. The experiment would verify that an
individual qubit stays coherent during the process of measurement (in contrast
to the gradual decoherence of the ensemble-averaged density matrix) thus
confirming the possibility of the qubit purification by continuous measurement.
The experiment can be realized using quantum dots, single-electron transistors,
or SQUIDs.
