On the capability of a class of quantum sensors

Quantum sensors may provide extremely high sensitivity and precision to extract key information in a quantum or classical physical system. A fundamental question is whether sensor capable of uniquely inferring unknown parameters system for given structure the admissible measurement on sensor. In this paper, we investigate capability class which consist either single qubit two qubits. coupled spin chain With initialisation schemes, employ similarity transformation approach Grobner basis method prove that single-qubit cannot effectively estimate while two-qubit can. The work demonstrates it feasible enhance by increasing number qubits some practical applications.