In this talk I consider a qubit system coupled to a stochastic classical field characterized by a 1/f^a spectrum (0.5 < a < 2) and address the decoherence and non-Markovianity induced by the external noise as well as the spectral characterization of the classical field by quantum-limited measurement on the qubit.
The unavoidable interaction of quantum systems with their complex environments usually destroys its coherence and quantumness. The fragile quantum information encoded in an open quantum system is lost due to the presence of the environment that continuously monitor the system. Decoherence may be induced by classical or quantum bath. The classical description becomes progressively more reliable as far as the environment has many degrees of freedom or when the interaction between a quantum system and a classical fluctuating field is taken into account. I thus analyze the dynamics of quantum correlations for two non-interacting qubits initially prepared in maximally entangled state and interacting with a classical colored noise generated by non-Gaussian processes. I also discuss the evaluation of non-Markovianity, in the sense of information backflow, of the induced dynamical map.
The precise characterization of the stochastic process generating the classical noise, possibly using minimal resources, is a crucial ingredient for the design of high-precision measurements and reliable communication protocols. To this purpose, I also address the characterization of the spectral parameters of classical noise by quantum probes, e.g. a qubit. I consider a system coupled to the stochastic process generating the noise and explore the performances of quantum measurements on the qubit to extract information about the spectral properties of the noise.