Quantum Metrology Based on Nonclassical Atomic States

Quantum measurements with atoms have been at the forefront of quantum technology and provide crucial information for a better understanding of quantum physics ever since their conception over a century ago. The universality of the quantized energy states of atoms makes the collective state of an atomic ensemble an outstanding platform for quantum-enhanced metrology. We introduce basic concepts regarding the metrological gain acquired from using nonclassical quantum states via multiparticle entanglement. Current challenges and future prospects for further enhancement of the measurement sensitivity through the use of nonclassical atomic states are discussed with reference to the shot noise and Heisenberg limits.