QUROPE Quantum Information Processing and Communication in Europe

We advocate a Bayesian approach to optimal quantum frequency estimation - an important problem for future quantum enhanced atomic clock operation. The approach provides a clear insight into the interplay between decoherence and the extent of the prior knowledge in determining the optimal interrogation times and optimal estimation strategies. We propose a general framework capable of describing the local oscillator noise as well as additional atomic dephasing effects. We also demonstrate an important fact: the average Bayesian cost can be expressed explicitly using the quantum Fisher information and thus establish a direct link between the two, often competing, approaches to quantum estimation theory.