Thermofield analysis of squeezing and statistical mixtures in quantum optics
Stephen Mark Barnett, P. L. Knight · Journal of the Optical Society of America B · 1985
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.