Quantum metrology and non-Markovian bath

Quantum metrology aims to enhance measurement precision beyond the standard quantum limit by taking advantage of certain non-classical states. However, decoherence induced by a bath will in general destroy quantum correlations underlying such states and hence nullify this quantum advantage. Here we show that a class of non-Markovian baths surprisingly preserves quantum correlations and results in stable non-classical states in steady state. We will provide a few specific examples. Our work demonstrate the application of reservoir engineering for quantum metrology.