  For open quantum systems, the Gaussian environmental dissipative effect can
be represented by statistical quasi-particles, namely, dissipatons. We exploit
this fact to establish the dissipaton thermofield theory. The resulting
generalized Langevin dynamics of absorptive and emissive thermofield operators
are effectively noise-resolved. The system-bath entanglement theorem is then
readily followed between an important class of nonequilibrium steady-state
correlation functions. All these relations are validated numerically. A simple
corollary is the transport current expression, which exactly recovers the
result obtained from the nonequilibrium Green's function formalism.

Statistical Mechanics