Quote by A. Neumaier
The thermal interpretation does not only apply to thermal states; it is completely general.
I suggest that you begin by reading the slides http://www.mat.univie.ac.at/~neum/ms/optslides.pdf
where the interpretation is explained for a single photon. The electron is essentially the same, except for the different state space.

Thanks. I still have more questions but let me ask you this. I understand you that you claim that the wavefunction and its derived probability is not real in standard QM interpretation, it is just a mashinary to interpret experiments. But, in QFT and QM any time we want to calculate something (like energy) we take the whole wavefunction into account which to me it says that all aspects of wavefunction (at least the probabilities) is real and it exists at the same time. Am I saying things correctly?