Improving parameters estimation in Gaussian channels using quantum coherence

Abstract: Gaussian quantum channels are relevant operations in continuous variable systems. In general, given an arbitrary state, the action on it is well-known provided that the quantum channels are completely characterized. In this work, we consider the inverse problem, i.e., the estimation of channel parameters employing probes in which quantum coherence is used as a resource. Two paradigmatic bosonic Gaussian channels are treated, the thermal attenuator and the thermal amplifier. We also consider the degradation of the coherence due to a Markovian bath. The quantum Fisher information for each relevant parameter is computed and we observed that the rate of change of coherence concerning the channel parameter, rather than the amount of coherence, can produce a parameter estimation gain. Finally, we obtain a direct relation between the quantum Fisher information and the relative entropy or coherence, allowing in principle an experimental implementation based on the measurement of the covariance matrix of the probe system.