In classical control, the measurement process is performed by various measuring instruments, and the transformation process is generally performed by the corresponding measuring sensor. The measuring instrument can be connected by a number of sensors in a suitable way to perform the transformation, selection, comparison and display functions together. As in classical control, the key to measurement in quantum control is the comparison between measured and standard quantities. The observable measurement in quantum control corresponds to the corresponding self-conjugation operator in quantum mechanics. The direct measurement of the state of quantum system is generally difficult to achieve. It is necessary to transform the measured measurement into a physical quantity that is easy to measure, and then realize the quantum state. Indirect measurement. This process can be done with a quantum sensor.