Quantum Metrology is one of the most promising application of quantum
technologies. The aim of this research field is the estimation of unknown
parameters exploiting quantum resources, whose application can lead to enhanced
performances with respect to classical strategies. Several physical quantum
systems can be employed to develop quantum sensors, and photonic systems
represent ideal probes for a large number of metrological tasks. Here we review
the basic concepts behind quantum metrology and then focus on the application
of photonic technology for this task, with particular attention to phase
estimation. We describe the current state of the art in the field in terms of
platforms and quantum resources. Furthermore, we present the research area of
multiparameter quantum metrology, where multiple parameters have to be
estimated at the same time. We conclude by discussing the current experimental
and theoretical challenges, and the open questions towards implementation of
photonic quantum sensors with quantum-enhanced performances in the presence of
noise.

简述：本文回顾了量子计量学的基本概念，特别关注光子技术在此任务中的应用，介绍了当今领域中平台和量子资源的最新进展，以及多参数量子计量学领域的研究方向，最后讨论光子量子传感器实施的实验和理论挑战，以及在噪声中具有量子增强性能的实现的未解决问题。