Key points are not available for this paper at this time.
We investigate the representation of mixed states in quantum optics by pure states in an expanded-state space. This thermofield representation is used to describe interactions involving thermal averages and, in particular, interactions involving parametric couplings. We find the thermofield representation of utility in the analysis of non-classical aspects of photon statistics, such as two-mode squeezing of light fluctuations.
Barnett et al. (Fri,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: