Review of qubit-based quantum sensing

The article presents a comprehensive review of qubit-based quantum sensing, highlighting the pivotal role of quantum sensors in achieving unparalleled sensitivity and precision in measuring both quantum and classical physical quantities. It explores various qubit systems, including spin-based systems, nitrogen-vacancy centres, and trapped-ion systems, and their applications in fields such as quantum cryptography, precision metrology, and quantum control. The review delves into the capabilities of single-qubit and multi-qubit sensors, discussing their structural design, measurement methodologies, and the fundamental question of whether data acquired from a quantum sensor can uniquely determine all unknown parameters of interest. The article also examines the Eigen-System Realization Algorithm (ERA) as a promising tool for solving Hamiltonian identification problems and the crucial roles of quantum entanglement and quantum noise in the performance and reliability of quantum sensors. Additionally, it provides an in-depth analysis of quantum noise, projection noise, and decoherence, offering insights into the practical considerations involved in implementing quantum sensing protocols. The review concludes with a discussion on quantum error correction codes and dynamical decoupling techniques, emphasizing their significance in enhancing the performance, reliability, and scalability of quantum technologies.