Distributed quantum sensing

A plethora of applications hinge on a network or an array of sensors to undertake measurement tasks. A rule of thumb for sensing is that a collective measurement taken by M independent sensors can improve the sensitivity by 1/M , known as the standard quantum limit (SQL). Quantum resources such as entanglement and squeezed light can be harnessed to surpass the SQL. Distributed quantum sensing is an emerging subject dedicated to investigating the performance gain enabled by entangled states shared by multiple sensors in tackling different measurement problems. This review formulates distributed quantum sensing (DQS) from a quantum-information perspective and describes DQS protocols and their experimental demonstrations. The applications enabled by DQS and an outlook for future opportunities will also be discussed.