The dynamics of a qubit reveals its coupling to a $N$ level system
  Modeling the environment of a single qubit as an N dimensional quantum system, we show that the dynamics of the qubit alone, if measured in sufficient detail, can reveal the parameters of the qubit-environment coupling Hamiltonian. We show that data from quantum process tomography experiments can be used to get information about the environment that can be used to minimize its deleterious effects on the state of the qubit. 
Vinayak Jagadish and Anil Shaji
quant-ph